TS 650 
.F5 





LIBRARY OF CONGRESS. 



Chap. Copyright No. 

Shelf.^E_£_ 



UNITED STATES OF AMERICA. 



GALVANIZING 



AND TINNING 



A Practical Treatise on Coating with Tin and Zinc 



WITH A 



Special Chapter on Tinning Gray Iron Castings 



BY 



W. T. KLANDKRS 



PUBLISHED BY DAVID WILLIAMS COMPANY 

232-238 William St., New York 

1900 



63375 



Litunu^f. of Con^Treea 



I'v^ CuftLij Received 
OCT 19 1900 



Cofvrighl entry 

SLCOND COPY. 

0(ftiver«d to 

ORDt« DIVISION, 
OCT 25 1900 



i^ |;i 



Copyrighted 1900 
By David Williams CoMPA>rY 



i 



y / 



In 1876 the firm I was employed by, finding it neces- 
sary to galvanize the goods they were manufacturing, 
placed the matter in my hands. Having little or no 
knowledge of the process, I spent considerable money in 
buying technical books that purported to treat on the 
subject, but found that what little they had to say was of 
no practical value whatever. I think the same condi- 
tions prevail now. Since 1889 I have made the installa- 
tion of galvanizing and tinning plants a business and have 
built nearly sixty. The increased demand for galvanized 
and tinned goods within the last ten years has brought 
me many requests from people for information regard- 
ing the two processes, and some four years ago I gave a 
brief description of the process of galvanizing in The 
Iron Ace and The Metal Worker. At the request of 
the publishers I have undertaken to describe the different 
methods of coating with zinc and tin by immersion. 
Having no previous work on the subject as a guide and 
being w^hoUy unused to writing, I realize that my work 
lacks the finish of most technical books. I think, however, 
that my treatment of the several subjects, coupled with the 
illustrations given, will enable one to make a successfui 
start in any of the processes. 

W. T. Flanders. 

Nashua. N. He 



CONTENTS. 

Page, 

Galvanizing j 

Locating a Plant and Selecting a Kettle 8 

The Galvanizing Room 8 

Tanks for Acids and Other Purposes lo 

Tools for Galvanizing 1 1 

Filling and Firing a New Kettle 13, 

The Use of a Pyrometer 13 

Materials Used in Galvanizing 14 

Building and Setting Kettles 15 

Removing vScale with Sulphuric Acid 23 

Cleaning Sandy Castings with Sulphuric Acid .... 24 

Preparing the Work for Dipping in the Zincing 

Bath 25 

Drying the Work 25 

The Heat of Zinc 27 

Dipping the Work in the Molten Metal 29 

The Formation of Dross in the Kettle 36 

Running Over, or " Sweating," Zinc Dross . 39 

Tinning Malleable Iron, Wrought Iron and Steel 43 

Preparing the Work 44 

Tools and Kettles 45 

A Tinning Plant 46 

Plan of Tinning Plant 48 

Removing Scale and Rust with Sulphuric Acid .... 50 



Page. 

Cleaning Sandy Castings by Sulphuric Acid 52 

Cleaning Sandy Castings with Hydrofluoric Acid . . 52 

Removing Paint or Grease 53 

Tinning with a Single Kettle of Tin 54 

Tinning with Two or More Kettles of Tin 55 

Passing the Work Through the Tinning Kettles. . 56 

Tinning Wire in Coils 5^ 

Tinning Steel Spoons and Similar Articles 59 

Retinning 60 

Setting Retinning Kettles 64 

Tinning Common Gray Iron 66 

Description of Tinning Plant 67 

General Considerations 69 

Tumbling Barrel 70 

Freeing Gray Iron Castings from Sand by Hydro- 
fluoric Acid 74 

Cleaning Sandy Castings with Sulphuric Acid. . . . 77 

The Use of a Hot Alkali Bath in Certain Cases .... 78 

Preparing the Castings in the Gas Barrel 78 

Coating the Castings with Tin 83 



GALVANiZiNG. 



The coating of articles of iron and steel with zinc, or^ 

as the process is generally known, *' galvanizing " them, 
as a means of retarding oxidation and for other reasons, 
has become a vast industry, in which a large number of 
men find employment. 

It is not our purpose to attempt a description of the 
methods emplo}'ed by the great manufacturers of gal- 
vanized sheets and wire, but to confine our efforts to the 
requirements of those who wish to engage in the business 
in a small way and to enable those whose location would 
otherwise compel them to ship goods long distances to 
erect and operate a plant of their own. 

It may not be out of place to say that it has been the 
practice of some engaged in the business to make as 
much of a mystery of it as possible. One fallacy given 
out and generally credited is that a galvanizing kettle 
must not be allowed to cool off. This, perhaps, has de- 
terred a greater number from attempting their own work 
than anything else. While it is true that it is not prac- 
ticable to allow a kettle holding several tons of metal to 
cool off every few days, there is no reason why a kettle 
containing a few hundred pounds of metal cannot be al- 
lowed to cool when it is not required for use. 

While it is our purpose to treat the subject in a way 
that will give a general idea of the whole business, our 
efforts will be mostly confined to explaining the methods 

T 



8 GALVAXIZIXG AND TIXXIXG. 

to be employed in galvanizing castings of gray and mal- 
leable iron, small articles of wrought iron and steel and 
sheet metal goods. 

LOCATIXG A PLAXT AXD SELECTING A KETTLE. 

To those contemplating the installation of a galvaniz- 
ing plant the first question that naturally comes up is, 
where can it best be located? In settling this question it 
should be kept in mind that the fumes of the chemicals 
used in the business are destructive to tools and machin- 
ery. For this reason the galvanizing plant should be in a 
building by itself. 

The next question is, what size kettle should be used 
and what is the best material to make it of ? On account 
of the difficulty in controlling the heat of a small body of 
metal, we would not advise the use of a kettle, for any 
purpose, less than 3 feet in length, 20 inches in depth and 
18 inches in width. The material for the kettle should be 
refined iron or best fire box steel, and should not be less 
than Yz inch thick. 

THE GALVAXIZIXG ROOM. 

In providing a room or a building in which to locate 
the plant, provision should be made to obtain good ven- 
tilation. It should be high posted and have a good ventila- 
tor in the roof, and if the character of the work to be 
done will admit, a hood may be built over the kettle, com- 
ing low enough to catch all the smoke possible, while not 
interfering with the movements of the operator. When 
the work is castings or small articles, there is no objection 
to having the hood come to within 6 feet of the floor, and 
it should be at least 2 feet larger than the brick work sur- 
rounding the kettle. 



GALVAXIZIXG. 



Considerable water is used in the process, and provi- 
sion should be made to secure proper drainage. A good 




Fig. 1.— Floor Plan of Galvanizing Room. 

plan is to put in a cement floor, which can be laid so as to 
provide gutters on each side of the room. If the work to 



lO GALVANIZING AND TINNING. 

be handled is castings it is not absolutely necessary to 
use steam, but if the work is of a nature that requires the 
removal of scale, steam should be brought into the room. 
A floor space 25 x 50 feet will accommodate such an 
outfit as we illustrate by Fig. i. A much less floor space 
can be made to accommodate a very small plant. Fig. i is 
the ground plan of a galvanizing plant, in which A is a 
tank for containing a solution of sulphuric acid and water 
for removing scale and rust. B is a water tank for stor- 
ing work that has been cleaned. C is a platform where 
castings are placed to free them from sand. D is a tank 
used to contain the solution for removing the sand from 
the castings after they have been placed on the platform. 
E is a tank for muriatic acid. F is the plate for drying 
the work before immersing it in the molten metal. G is 
the kettle containing the metal and H is the tank used for 
cooling the work after it is coated with the zinc. I I in- 
dicate the loose planks covering the ash pits, shown in 
Fig. 3 as M INI. K is an underground flue connecting the 
drying plate F with a chimney or stack. L, and M is a pit 
to give access to the ash pit under the plate F. 

TANKS FOR ACIDS AND OTHER PURPOSES. 

The illustration, Fig. i, shows wooden tanks, to be 
built as shown in Fig. 12. When this style of tank is em- 
ployed the bolts, in those designed for acid, should be of 
•copper. Pine or cypress makes good material for tanks. 
It is by no means necessary to build expensive tanks if 
the work to be done is small articles. If oil barrels are 
sawed in half and thoroughly cleaned they answer every 
purpose, provided, of course, that the work is of a size 
that half barrels will accommodate. 

It used to be considered necessarv to line acid tanks 



GALVANIZING. 



II 



with lead. The experience of the writer is that it is 
money thrown away. The practice has been almost en- 
tirely abandoned. 

TOOLS FOR GALVANIZING. 

The tools employed in galvanizing usually consist of 
tongs of various shapes and sizes, baskets of sheet iron or 
heavy wire cloth, and wires bent in various shapes. The 
necessary shape of the tongs will be suggested by the 




Fig. S. — Top View of Large Galvanizing Kettle. 



shape of the article to be handled. In Fig. 13 we illus- 
trate the shape of baskets and wires most generally in 
use. B is a sheet iron basket having a handle about 3^ 
feet long. 1 he basket should be about 8 inches in diam- 
eter at the top and 7 inches at the bottom, with a depth of 
9 inches. Both the bottom and body should be well per- 
forated to allow the metal to pass out. This style of 
basket is well adapted to galvanizing nails and other small 
articles, and the holes should be of a size that will not ad- 



12 



GALVANIZING AND TINNING. 



mit of the articles being handled falling through. A is 
a basket made of heavy wire cloth, the body being about 
8 inches wide, lo inches long and 6 inches deep. This 
basket is adapted to large work that cannot be strung on 
wires and is too small to be handled singly with tongs. 



M 



M 




'i\^^^////} 



^ 






c c 

Fig. S.— Section of Fig. 2 at A\ A\ 




Fig. 4.—Side Elevation of Large Galvanizing Kettle 



E and G are wires for handling small work in the molten 
metal. F is a scoop for removing the dross from the bot- 
tom of the kettle. D and H are skimmers, and E is a hook 
to suspend in the molten metal articles that are strung on 
wires. The use of all will be explained in their turn 



GALVAXI.ZIXG, 13 

Most of these tools are adapted to use in tinning as well 
as galvanizing. 

FILLING AND FIRING A NEW KETTLE. 

In filling a kettle for the first time with the pigs of 
zinc, or, as it is termed in the trade, " spelter," place the 
metal in a way that it will lie as closely as possible to the 
sides of the kettle, and also arrange it so that as the 
outside slabs of metal melt those next to them will be 
forced against the sides of the kettle. Unless this is done 
the kettle is apt to be injured by the heat. Do not allow 
the fires to burn too freely in melting a kettle of zinc or 
in firing up a kettle that is full of cold metal. In melting 
a kettle of metal for the first time keep the fires about even 
with the molten metal in the kettle, allowing them to rise 
in about the same proportion as the metal melts. Do not 
use the top drafts until the molten metal is about even 
with them. 

THE USE OF A PYROMETER. 

A good pyrometer placed in the kettle will be found 
of great value in keeping the bath at a uniform temper- 
ature. Unless, however, the stem of the pyrometer is 
protected from the action of the metal it will soon be de- 
stroyed. The writer has devised a means by which the 
stem of the pyrometer is kept from contact with the 
molten zinc and at the same time gives the same result as 
though the molten zinc w^as in direct contact with the 
pyrometer stem. 

The arrangement consists of a piece of 2-inch pipe 
about 20 inches long, with one end closed tight. The top 
of the pipe is provided with a bushing, with a hole a little 
larger than the stem of the pyrometer. A second bushing 
should also be placed in the pipe about 3 inches from the 



14 



GALYANIZINr. AND TTMMTMn 



bottom. These bushings serve to keep the pyrometer in 
an upright position. The casing surrounding the stem of 
the pyrometer is filled with lead, so that when the arrange- 
ment is placed in the kettle there is a direct metal connec- 
tion with the stem of the pyrometer. Fig. 14 shows a py- 
rometer in position in the kettle, while Fig. 15 shows the 
" protector " in detail. 

MATERIALS USED IN GALVANIZING. 

The principal materials used in galvanizing are zinc. 




Fig. 5 — Section at Grate Line of Large Oalvamzing Kettle 

sal ammoniac, muriatic, sulphuric and hydrofluoric acids 
and gas coke. We cannot with fairness express a prefer- 
ence for any brand of spelter, and will only say, use spel- 
ter smelted by a reliable firm, keeping in mind that much of 
the so-called spelter is recovered from zinc dross by par- 
ties who do not have the facilities for doing the \vork 
properly. The best sal ammoniac to use is the " gray 
granulated," although the " white granulated " answers 
every purpose. 



GALVANIZING. 



15 



BUILDING AND SETTING KETTLES. 

In deciding what size kettle to put in you must be 
guided by the nature of the work to be done. If it is 
small articles that are to be handled, and the amount such 



O 



O) 



■\2y 



c 



^ 



E 



K 



Et- 



Lt,;;, " ■■{ 



Uj 



I^ 



H 



Fig. 6.— Casting Details of Large Galvanizing Kettle. 

as will only require the plant to be operated at intervals, 
a kettle 3 feet long, 18 inches wide and 20 inches deep 
will answer the purpose. A kettle more than 20 inches 
deep makes it necessary to provide ash pits at the sides, 
as shown in Fig. 3 and designated M M. 



n^ 



i6 



GALVANIZING AND TINNING. 



In Figs. 7, 8 and 9 we show method of setting a small 
kettle that is not designed to be operated continually. The 
grates C C in Fig. 9 are bars of iron that may be with- 
drawn when it is desired to let the fire out and replaced 
when required for use. 

Figs. 2, 3, 4 and 5 show manner of setting kettles 5 feet 
long and upward, and Fig. 6 gives the casting details. 
Fig. 10 gives shape and construction of kettle. The rivet- 









A 




I i . 


A 




. 


-H a 




1 1 

1 1 
1 1 
1 > 

1 1 





Fig. 7. — Top Plan of Small Galvanizing Kettle. 



ing in the heads may be spaced 2J/2 inches, while the 
rivets securing the stiffening bars to the sides may be 
spaced 4 inches. For kettles from 4 to 6 feet in length 
material % inch thick will answer for the body and ^ 
inch for the heads. Above 6 feet material at least i inch 
thick should be used. 

Fig. 10 shows a kettle in which the body is formed of 
one piece, and with the rivets where the fire will not affect 
them. A kettle for general use built after this illustration 



GALVANIZING. 



17 



is our preference for many reasons, but it does not follow 

that the work could not be done in a kettle of any shape. 

A, Fig. 6, are the coping plates, the position of which 

is shown in Figs. 2, 3 and 4. These plates, when held in 




Fig. 8.— Section of Fig. 7 at A', A, 




Fig. 9. — Section of Small Galvanizing Kettle, Showing Method 

of Setting Grates. 

place by the bolts C, serve to preyent the sides of the 
kettle from springing outward when the iron blocks D D 
are in place, as shown in Figs. 2 and 3. Coping plates 
for kettles from 4 to 6 feet long should be 2y^ inches 



i8 



GALVANIZING AND TINNING. 



thick and lo inches wide. The fire spaces E E in Figs. 2 
and 3 should not be more than 7 inches wide and the same 
length as the inside of the kettle. 

D in Fig. 6 are the blocks designated in Figs. 2 and 3 
as D. F in Fig. 6 are the iron plates i inch thick. Their 
positions are designated in Figs. 2 and 3 as F. G in Fig. 
6 is a section of grate, the position of which is designated 
in Figs. 3 and 5 as G G. The openings of this grate 
should be about i inch wide and the grates should be wide 




Fig. 10. — End and Side Elevations and Top View of Large 
Galvanizing Kettle. 



enough to span the fire spaces E E in Figs. 2 and 3 and 
rest on plates H H and the pier I, on which the kettle B 
rests, as shown in Fig. 3. The plate H in Fig. 6 may also 
be used to cover the fire spaces E E, Figs. 2 and 3. The 
plates should be about 3^ inch thick and 12 inches wide; 
their length is determined by the length of the kettle. K 
in Fig. 6 is the casing for the upper draft holes indicated 
as K K in Figs. 3 and 4. The casing should be about 10 
inches long, with the opening about 4x4 inches. It 
should be arranged to close with a slide, as shown in Fig. 



GALVANIZING. 



19 



4. L in Fig. 6 shows the casings for the lower set of 
drafts, the openings in which should be 8 x 12 inches. 
Their position in the brick work is designated in Figs. 3, 
4 and 5 as L. Fig. 2 is a top plan of the brick work. Fig. 
3 is a vertical section at A' A' and Fig. 4 is a side ele- 
vation. 

The ash pits M M, in Fig. 3, should be about 2 feet 
wide. The pits are covered with loose planks, so that 
access to the lower drafts may be had for the purpose of 



000 




Fig. 11. — Casting Details of Small Galvanizing Kettle. 



opening or closing them, and also for the purpose of re- 
moving the ashes from the spaces N N under the grates 
G G, Fig. 3. 

Fig. 5 is a horizontal section of the brick work at the 
grate line and shows the grates G G in position, and also 
the manner of laying the bricks between the draft casings 
L L. I indicates the pier on which the kettle rests. It 
will be seen that the brick work between the lower draft 
casings L L is built in a way to allow all the access possi- 
ble to the grates G G from the ash pits M M. The plates 



20 



GALVANIZING AND TINNING. 



H H are used to test the outer edge of the grates G G on, 
and also to support the brick waUs at each side of the 
kettle. The walls on each side of the kettle should have 
a lining of fire brick commencing at the grate and ex- 
tending upward to the coping plates A A, Fig. 3. 

Figs. 7, 8 and 9 show manner of setting a kettle that 
is not deep enough to require ash pits at the sides. For 




■i i 



J 



Fig. 13.— Details of Acid Tank. 



casings for the upper and lower drafts make the patterns 
as shown in Fig. 6 and which are designated K and L. 
Fig. 7 is a top plan of the brick w^ork surrounding the ket- 
tle. Fig. 8 is a vertical section of Fig. 7 at A' A', and 
Fig. 9 is a horizontal section at B' B'. 

Fig. 6 shows all the casting details necessary to set a 
kettle in the manner shown in Figs. 2, 3, 4 and 5. The 
bolt C that sets in the brick work vertically is provided 
at one end with a foundation washer, B, which is held in 
place by the key E, The positions of the other castings 



GALVANIZING. 



21 



in this figure are all shown by corresponding letters in 
Figs. 2, 3, 4 and 5. 

Fig. II gives the casting details necessary to set a ket- 
tle after the plan shown by Figs. 7, 8 and 9. A is a plate 




Fig. 13 — Galvanizing Tools. 

to cover the top of the brick work surrounding the kettle, 
and its position is designated in Fig. 7 as A. B is a cast- 
ing used in connection with bolts passing through the ends 
to bind the brick work together. Its position is desig- 
nated in Fig. 8 as B. C is the grate, the position of which 
is shown in Fig. 9 at C, and D, Fig. 11, are the castings 



22 



GALVANIZING AND TINNING. 



for supporting each end of the grates C, the position of 
which is designated in Figs. 8 and 9 by D. 

A kettle for galvanizing pipe should be 23 feet long, 
3 feet deep and 2 feet wide. One for sheet iron ware, if 
it is intended to include washtubs and garbage cans, 
should be 6 feet long, 3 feet wide and 4 feet deep. Coal 
hods can be galvanized in a kettle of the size shown in 




Fig. 14. — Perspective of Oalvanizing Kettle, Showing 
Position of Pyrometer. 



Fig. 2 — viz., 6 feet long, 3 feet deep and 18 inches wide. 
A kettle designed especially for galvanizing wire should 
be II feet long, 2 feet deep and 2 feet wide. Wire cloth 
and poultry netting is best run in a kettle 6 feet long, 4 
feet wide and 2 feet deep. 

In bricking in a kettle use care to protect all the calked 
joints from the fire and do not make the fire spaces too 
wide. If too much space is left for fire the heat of the 
metal cannot be kept under control. 



GALVANIZING. 



23 



REMOVING SCALE WITH SULPHURIC ACID. 

Nearly all articles made of wrought iron or steel or of 
sheet metal are covered with more or less heavy scale, 
which must be completely removed before the zinc will 




Fig. 15. — Pyrometer " Protector " in Detail 

adhere. To accomplish its removal make a pickle of 
sulphuric acid and water, i part acid to 20 of water, and 
bring the solution to a temperature of about 150 de- 
grees F. 

The length of time required to accomplish the work 



24 GALVANIZING AND TINNING. 

varies with the thickness of the scale. In many cases it 
is necessary to remove part of it with some sharp pointed 
tool. When the material has been burned in welding, 
and where the scale has been rolled deeply into the stock, 
it is necessary to use a tool to loosen the scale. Stock 
having an uneven coating of scale should be cleaned in a 
w^eaker solution than that having an even coating or than 
that having a light scale. The reason is that that part 
of the stock which is first made clean will be overpickled 
before the parts having the heavier scale are clean. 

When the work seems perfectly clean and free from 
scale or rust it should be put into a tank containing water 
enough to cover it completely. A, in ¥ig. i, designates 
the tank to be used for treating the material to remove 
the scale, and B in the same illustration denotes the stor- 
age tank. 

CLEANING SANDY CASTINGS WITH SULPHURIC ACID. 

Castings that are sandy may be cleaned by pouring 
over them a solution of sulphuric acid and water, i part 
acid to 6 of water. Place the castings on the platform 
C in Fig. I and wet them with the solution which is con- 
tained in tank D, Fig. i. Continue this operation until 
the sand will wash ott by the application of water. The 
castings should be wet every hour or so, and they should 
be cleaned in about 12 hours. 

Cast iron that has been allowed to remain in the pickle 
too long will be covered with a gummy or greasy sub- 
stance, and will not properly take the coating of zinc un- 
less it is left in the metal a long time, and even then it will 
not be nicely coated, but will be rough and covered with 
thick patches of metal. It will not have the gloss that a 
properly prepared casting will have. We refer to this 



GALVANIZING. 2^ 

method of cleaning sandy castings in the chapter on tin- 
ning, and it will be well to read what is said there in this 
connection, as the rules there given apply to galvanizing, 
as well as what is said regarding dry tumbling as an aid 
in cleaning work for tinning. 

PREPARING TIIK WORK FOR DIPPING IN THE ZINCING 

BATH. 

To enable the zinc to take to the work quickly and 
firmly a solution of muriatic acid and water is used. This 
not only serves as a flux, but it removes any rust that has 
formed on the work in the operation of inspecting and 
removing the scale or sand that the sulphuric acid pickle 
failed to remove. If the work has been thoroughly 
cleaned by dry tumbling the use of sulphuric acid is not 
necessary. If no rust has formed on the work all that is 
necessary is to immerse it for two or three minutes in this 
muriatic solution. If rust is present it must be immersed 
long enough to remove it. 

Some galvanizers use full strength acid for this pre- 
paratory dip, but we prefer to dilute the acid about one- 
half and to add i pound of sal ammoniac to a gallon of the 
mixture. Tank E, Fig. i, is for containing this mixture. 

DRYING THE WORK. 

From tank C, Fig. i, or, in other words, from the 
muriatic acid, the work is taken to the place provided for 
drying it. The position of this drying arrangement is 
designated F in Fig. i. This drying arrangement may 
be the plates covering the fires that heat the kettle. If 
the work to be handled only amounts to a few hundred 
pounds per day it can be dried in this way. If, however, 
the amount of work necessitates keeping the kettle in con- 



26 



GALVANIZING AND TINNING. 



stant Operation, a drying arrangement such as shown ia 
Figs. i6, 17 and 18 should be provided. Sheets and pipe 
should be dried in an oven. 




Fig. 16. — Perspective View of Drier. 




Fig. 17 .—Horizontal Section of Fig. 16 at Orate Line, 




•mzmzs2^zs:2Z2. 










Fig. 18.— Vertical Section of Fig, 16. 

The location of this drying arrangement is a mere 
matter of choice. In Fig. i we show it located at one 
end of the kettle. The work should be perfectly dry, but 
it should not be allowed to get hot enough to burn the 



GALVANIZING 21 

acid. When properly dried the muriatic acid should 
show on the surface of the work in the form of a white 
powder. Work that has been prepared for dipping and 
dried should not be allowed to get cold, and if more has 
been prepared for dipping than can be finished it should 
not be allowed to remain on the drier over night, but re- 
turned to the water tank. It should, of course, be re- 
dipped in the muriatic solution and dried again before 
putting it into the zincmg kettle. 

Figs. i6, 17 and i8 show a good arrangement for 
drying the work. Fig. i6 is a perspective view of the 
completed work, Fig. 17 is a horizontal section of Fig. 16- 
at grate, and Fig. 18 is a vertical section. 

THE HEAT OF THE ZINC. 

This part of the business is not only the most difficult 
to describe, but it is the most difficult to learn, for the 
reason that different kinds of work require that differ- 
ent temperatures be maintained. A kettle of zinc at the 
proper heat for wire or wire cloth would be much too hot 
for galvanizing castings of either gray or malleable iron, 
while with the zinc at the proper heat for large work it 
would be impossible to coat small work properly, even if 
the material was the same. Large pieces require that a 
low heat be maintained on the zincing bath. Small work 
that is strung on wires for dipping requires a higher heat 
of the zincmg bath than heavy pieces. Work that is gal- 
vanized in baskets requires a higher heat of the zincing 
bath than work that is strung on wires and drawn from 
the coating bath without the aid of a flux on the surface 
of the molten metal, as hereafter described. 

We shall give the degrees of heat that a pyrometer 
should indicate when different kinds of work are being 



28 GALVANIZING AND TINNING. 

done, basing the rules given on the supposition that when 
the metal is barely melted — that is, at a temperature that 
would just keep it in a liquid state, the pyrometer indicates 
750 degrees of heat. We shall also give the best rules 
possible for determining the proper temperature by the 
looks of the metal and by other signs. 

Large gray iron castings require that the metal be at 
the lowest temperature possible and have it liquid. At 
about this temperature it will be silver white in color, will 
burn sal ammoniac slowly when thrown on its surface, and 
when a skimmer is passed over its surface the oxide will 
be slow in appearing. In this condition the pyrometer 
should indicate about 775 degrees of heat. This tem- 
perature is also suitable for galvanizing very thin castings 
that it is designed to " spangle " or to have a crystallized 
appearance — for example, sinks and like work. 

For small castings that are to be drawn through the 
metal without using a flux the pyrometer should indicate 
about 840 degrees. At this temperature the metal should 
have a slightly bluish cast, burn sal ammoniac moderately 
quick and show the oxide in a few seconds after the 
skimmer has been passed over its surface. This tem- 
perature is about right for galvanizing wrought iron pipe ; 
the cheaper grades of sheet iron or goods made from it, 
such as coal hods, ash cans and chamber pails. Heavy 
malleable iron castings will also coat nicely at this heat. 

For small work, such as nails and. in fact, almost any 
work that is done in baskets or strung on wires and drawn 
through a flux, the pyrometer should indicate from 870 
to 890 degrees of heat. The metal should burn sal 
ammoniac quickly and oxidize quickly. It will be quite 
blue in color. This temperature is about right for sheet 
steel and articles made from it, as well as steel pipe. 



GALVANIZING. 29- 

DIPPING THE WORK IN THE MOLTEN METAL. 

We will describe the manner of handling several dif- 
ferent articles as a general guide for handling all kinds 
of work. Considerable skill is required to bring a piece 
of work out of the metal and cool it so that the surface 
will be smooth, free from blisters and with no lumps of 
surplus metal attached. 

Before dipping the work, cover the surface of a part 
of the molten zinc with a flux of sal ammoniac to keep the 
oxidized metal from adhering to it. To prepare this flux 
sprinkle a few handfuls of sal ammoniac on the surface of 
the molten metal, and as soon as it is melted add a few 
drops of glycerine. This will cause the flux to thicken 
up and will prevent it. in a measure, from covering the 
entire surface of the metal. The glycerine also causes 
the flux to remain stationary, so that when the operator is 
ready to draw the article from the bath the flux will not 
cover the space he has cleared with his skimmer for that 
purpose. The tool designated D in Fig. 13 is used for 
the purpose of skimming the surface of the metal before 
drawing the v\-ork from the bath. 

This flux not only prevents the zinc from oxidizing, 
but it assists the metal to take quickly and evenly to the 
work. Keep the flux fresh by adding more sal ammoniac 
from time to time. 

We will suppose the article to be dipped is a cast iron 
s-ink or some similar casting — that is, a thin casting. 
Have the metal at the temperature first described under 
the heading " The Heat of the Zinc." After satisfying 
himself that the casting is perfectly dry and hot enough to 
have expelled all moisture from it the operator catches the 
article with a pair of tongs and plunges it as quickly as 
possible, and not cause the metal to spatter, into the mol- 



3© GALVANIZING AND TINNING. 

ten zinc. He must hold the article beneath the zinc until 
it is as hot as the zinc itself. After the article has been in 
the bath a few minutes it should be rinsed around in the 
metal in such a way that the flux floating on the surface 
of the molten zinc will come in contact with all parts of it. 
When the article is thoroughly coated clear a space on the 
surface of the molten zinc with the skimmer, and after 
dusting on a very little dry powdered sal ammoniac draw 
the article from the metal. 

In performing this operation catch the article with 
the tongs in such a way that the part they grasp will be 
the last to leave the metal. Do not lift the article clear 
cf the metal with the tongs you use in the metal, but pro- 
vide a second pair to handle the article with until it is 
cooled. In drawing the article raise it slowly with the 
tongs held in the position described, and as soon as it is 
partly clear of the metal grasp it with the tongs provided 
for that purpose, and complete its removal. Hold the 
article in such a position as will admit of the metal flowing 
to one point, and just as the drop is about to harden re- 
move it with a stiff brush or an old file. Expose the ar- 
ticle to the air until crystals appear, and then brush it 
vi^ith a brush wet in clear water. Do not dip the article 
in water, especially if it is a sink or a very thin casting, as 
that would be quite likely to break it. In any event the 
coating would not be as bright as it would be if left to cool 
gradually after brushing with the wet brush. Thick 
heavy castings may be dipped in water at once on remov- 
ing them from the molten metal. 

Coal hods and similar goods of sheet steel or iron only 
require to be left in the bath a few seconds. The flux 
through which they pass should be confined at one end of 
the kettle by a piece of sheet iron long enough to go across 



GALVANIZING. ;^l 

the kettle from side to side. This is called a " flux guard," 
and it should enter the metal about 2 inches, with the 
upper edge as high or a little higher than the sides of the 
kettle. In galvanizing sheet metal ware the flux should 
be made to foam up nearly to the top of the kettle by using 
glycerine. The goods should be passed through this flux 
into the metal, and as soon as they are coated, which will 
be in a very few seconds, they must be passed under the 
flux guard to the end of the kettle that is kept free of flux. 
In passing the article under the flux guard keep the open- 
ing up so that none of the flux will be carried along with 
it. Remove the article from the metal in the way just de- 
vScribed for sinks and similar articles, but do not sprinkle 
the surface of the zinc with sal ammoniac. Allow the 
work to cool in the air. If any particles of the sal am- 
moniac have adhered to the work in drawing it from the 
molten metal remove them with a wet brush. 

Some articles can be galvanized very nicely by string- 
ing them on stout wires about i ^ feet long. When this 
method is employed string on a number of the pieces, and 
then bring both ends of the wire together and clinch them 
securely. To suspend work in the metal strung this way 
use a hook, shaped after the form given in Fig. 13 and 
designated C. Provide several of these hooks, so that a 
batch may always be ready when the previous one is re- 
moved from the kettle. A piece of ^-^-inch round iron, 
bent in the shape of the letter S, will serve to remove the 
strings of castings from the hooks, and also for handling 
them after they are removed. The wires E and G, Fig. 13, 
are intended for stringing small articles on for the pur- 
pose of dipping them in the molten metal. 

In handling small articles on these wires use a motion, 
after thev are drawn from the metal, calculated to free 



32 GALVANIZING AND TINNING. 

them of surplus metal and also to prevent their adhering 
to each other when they are plunged in the water. To do 
this properly will require some practice. 

It is a good plan to warm the cooling water slightly 
for cooling some articles, and to have a thin film of oil on 
the surface. Small articles strung on wires may be drawn 
through the metal after sprinkling on a small quantity of 
powdered sal ammoniac, or may be drawn through a clear 
thin flux of sal ammoniac, to which a few drops of glycer- 
ine have been added. If the latter plan is used, as it should 
be if the articles are such as are liable to rub and stick 
together, the oil should not be used on the cooling water. 

Small work that cannot be strung on wires may be 
galvanized by using a basket of wire or sheet iron. We 
have already described these, and they are designated in 
Fig. 13 as A and B. 

When these baskets are employed the flux should be 
of a consistency that will run freely among the work. A 
block of iron should be placed in a position beside the 
kettle that will permit the operator to rest the handle of 
his basket over the block with the basket hanging over 
the kettle. Using this block as a rest, the operator should 
shake the basket sharply, and for several seconds, to free 
the work of surplus metal, and when it is accomplished 
he will shake them into the water to cool them, after which 
dry them off by dipping them in boiling water and then 
throwing them into sawdust. Nails or tacks may be 
shaken out of the basket onto an iron plate, placed at an 
angle, over a tub of water. The plate should be inclined 
sufficient to allow the work to slide into the water readily. 

Sheet iron, wire, wire cloth and poultry netting are 
mostly passed through the zincing bath mechanically, and 
as the means employed are too expensive and complicated 



GALVANIZING. 



to illustrate or describe we shall not attempt it. Sheet 
iron may be, and once was. galvanized by parting the ket- 
tle lengthwise with a tlux guard. The side where the 
prepared sheet enters the bath is covered with a sal am- 
moniac flux, and the opposite side, where it leaves the bath, 
is covered with coke dust to the depth of about i inch.' 
A light single block and fall is used to assist in drawing 
the sheet from the kettle, and every kettle in which work 
of large size is galvanized should be so provided. 

Wire cloth, wire and poultry netting may be galva- 
nized by running it through the kettle by means of a reel. 
In galvanizing wire cloth and poultry netting the kettle 
should be parted by a fiux guard, as previouslv described 
and the coke dust piled up to a depth of several inches and 
kept sprmkled with water by using an ordinary watering 
pot. 1 he flux should be present where the work enters 
the metal. 

Wire requires no flux at the point where the work 
enters or on any other part of the kettle. Sand or coke 
dust or dies of asbestos may be used to wipe off the sur- 
plus metal. If the kettle for wire is the usual length of 
10 teet the wire may be drawn through the metal at a 
speed of about 75 feet per minute. If it is being done in 
a short kettle the speed must be slow enough to allow the 
work to be perfectly coated. 

In Fig. 19 we give the position of the different pieces 
of apparatus required to do the work in a small' way 
Large plants equipped to do this work exclusivelv are 
fitted with reels driven by power, and several strands are 
run through simultaneously. In Fig. 19 A is the position 
of the reel holding the black wire, B is the tank holding 
the muriatic acid, C is the kettle, D a tank containing 
water and E the position of the reel for drawing the wire 



GALVANIZING AND TINNING. 



•I 

I 



CO 

I 

o 









GALVANIZING. 



35 




Fig. SO.— Perspective of Dross Kettle. 




Fig. 21.— Top Plan of Dross Kettle. 



36 



GALVANIZING AND TINNING. 



THE FORMATION OF DROSS IN THE KETTLE. 

The waste caused by the formation of dross is quite 
large, even with an experienced man in charge of the ket- 




Fig. ^2— Vertical Section of Fig, 21 at A. A, 




Fig. S3.— Horizontal Section of Fig. 22 at Grate Line. 

tie. The amount of dross made is increased by faihire in 
keeping the metal at a temperature that will not injure it, 
by allowing the work to be lost in the kettle and through 



GALVANIZING. 




37 



t^^^^^^^^^^^ 



-tAVVXV^V^^,^^^ 




Fig. ^4>— Details of Dross Kettle. 



38 GALVANIZING AND TINNING. 

immersing in the kettle work that has not been properly 
prepared. 

As the dross forms it settles at the bottom of the kettle, 
and when the accumulation is such that it interferes with 
the work it must be removed. As the dross settles it be- 
comes hard, and is easily removed by the proper appliance 
for that purpose. The tooj for removing the dross is 
called a " dross scoop." In Fig. 13 we show the shape 
of this tool, designated F, where a round bottom kettle is 
in use. The handle of the scoop should be about twice 
the length of the kettle, unless the kettle is of a size that 
requires the use of tackle in drossing it. The scoop 
should be well perforated to allow the clear metal to flow 
back into the kettle. In removing the dross use care not 
to stir or rile more than possible when forcing the dross 
scoop into the hardened mass. Force the scoop into the 
dross gently, and when you are satisfied that the scoop 
is full, raise it out of the metal by resting the handle of 
the scoop on the end of the kettle to get a leverage. Let 
the scoop remain over the kettle until all the clear metal 
that will has dripped back into it. If the handle of the 
scoop is rapped with a hammer or piece of iron it will 
cause more of the clear metal to separate from the dross 
than would be the case if it was not done. As soon as 
the clear metal has ceased to drip dump the dross into cast 
iron pans. These pans should be about 2 inches deep, 15 
inches long and 9 inches wide. 

Dross hardens very rapidly when exposed to the air, 
and no more time than is necessary to allow all the metal 
possible to drip back into the kettle should be consumed 
in getting it into the dross pans. 

If there is a large amount of dross in the kettle and it 
is desired to allow the fi-res to go completely out it should 



GALVANIZING. 



39 



be removed. If the kettle is allowed to cool with a large 
amount of dross lying in the bottom of it the result will 
most likely be a burst kettle. Before commencing to 
dross the kettle — that is, remove the dross — skim all the 
flux from the surface of the metal with a perforated 
skimmer. This tool is shown in Fig. 13, and is desig- 
nated H. 

RUNNING OVER OR " SWEATING '' ZINC DROSS. 

The writer is often asked if it pays the galvanizer to 
try and recover the good metal from the dross, and how 
best to accomplish it. \\' ithout entering into a discussion 
regarding the desirability of attempting its recovery, from 
a financial point of view, we will say that it is our prac- 
tice to " sweat " our dross. 

In Fig. 20 we give a perspective view of the kettle 
and brick work for running over dross. Fig. 21 is a top 
view, Fig. 22 is a vertical section at A A and Fig. 23 is 
a horizontal section at the grates. The kettle and casting 
details for bricking in are shown in Fig. 24. The ar- 
rangement is so simple that we do not think it necessary 
to describe it in detail. 

The kettle should be made of cast iron, with the bot- 
tom about I inch thick. A kettle 30 inches in diameter 
and 20 inches deep answers the purpose very well. 

To separate the good metal from the dross first melt 
up about 6 or 8 inches of lead in the bottom of the kettle 
and then put in the dross. Bring the dross to a temper- 
ature that will cause it to have rather a dark blue color 
or where the pyrometer will register about 1050 degrees. 
When this is accomplished stir the mass with a long 
handled ladle for about one-half hour, and then allow it to 
settle. When the mass has settled the lead will be at the 



40 GALVANIZING AND TINNING. 

bottom, the dross will lie on the lead and the clear metal 
will be at the top, where it can be bailed out into pans. 
The stirring may be repeated once or twice after each 
bailing- operation. After all the clear metal has been ex- 
tracted that can be remove the dross and put it into pans. 



TINNING IRON AND STEEL 



41 



TINNING MALLEABLE IRON, 

WROUGHT IRON AND STEEL 

Simply to give articles of malleable and wrought iron 
a coating of tin is a comparatively easy process to master, 
but tinning on certain articles of hardware has reached a 
high state of perfection, and to tin saddlery hardware and 
the cheaper grades of table cutlery requires considerable 
skill. The methods employed to do the work vary greatly 
in different establishments, and the degree of perfection 
attained is equally at variance. Work that is tinned in an 
indifferent and slovenly manner is not necessarily done 
cheaply, as the material wasted on an article roughly and 
imperfectly coated is of more value than the slight saving 
in labor cost obtained by rushing the work through without 
proper attention to obtaining a light and even coating. 
The high price of the metal used to tin articles makes 
the cost of the material much more than the labor cost. A 
loss of TO per cent, of the material by careless handling 
would represent a much larger proportion of the entire 
cost of the work than would an increase of the same per 
cent, added to the labor cost. Painstaking in bringing 
out the finished article free from surplus tin not only 
adds greatly to the commercial appearance of the goods, 
but materially decreases the cost of the work. This eco- 
nomical result is reached by careful attention to the heat 
of the tinning bath and to the skillful handling of the 
articles after their removal from the tinning pot and be- 

43 



44 GALVANIZING AND TINNING. 

fore they are cooled. If the tin is not hot enough the 
articles will be heavily coated, and it will cool on the work 
l3iinchy and wavy. A degree of heat above a certain 
limit also causes the work to have a rough and uneven 
appearance, injures the color and destroys the luster. 
The use of a good pyrometer in a tinning bath is a great 
help to the operator in maintaining a uniform heat of the 
tin. 

PREPARING THE WORK. 

Ordinarily the common grades of tinned articles are 
made ready for tinning by simply removing the sand, scale 
or rust by an application of either commercial sulphuric, 
muriatic or hydrofluoric acid. The finer grades of work 
are prepared for tinning by careful and lengthy rolling 
in gravel and water. This preparation not only effect- 
ually removes all impediments to a perfect coating, but 
gives the articles a smooth and perfect surface on which 
to deposit the tin, the degree of perfection obtained being 
determined by the time and care expended in the rolling 
operation. 

A piece of wrought iron from which the scale has been 
removed by the application of acid will not have the 
smooth and perfect coating that the same would have if 
the removal of the scale was accomplished by irritation. 
The same is true of articles of malleable iron. The best 
and most perfect results are obtained by giving the cast- 
ings a thorough tumbling in gravel and water, which 
operation brings the surface of the castings to a state of 
smoothness only equaled by buffing or grinding. ]Mal- 
leable castings on which it is desired to obtain a fine fin- 
ish should invariably be given this treatment. It is, of 
course, necessary that the patterns from which castings 



TINNING. 45 

are taken that are designed to be tinned be made with a 
view to obtaining- the smoothest surface possible as an 
assistance to the tumbHng operation. 

Some tinners not only roll their castings in gravel and 
water, but for the purpose of obtaining a still finer surface 
than can be obtained by this method they roll them in 
dr}-, coarse sand, and also give them a third rolling with 
scraps of leather, the entire operation often requiring 30 
or 40 hours in going through the several treatments. 
Water rolling is so conmion and so thoroughly understood 
that we consider it unnecessary to go into detailed instruc- 
tions regarding the apparatus to be used or the methods 
to be employed. There are several concerns who make 
the manufacture of rolling barrels for this purpose a spe- 
cialty, and the cheapest method to adopt in equipping a 
tinning plant with wet rolling barrels would be to buy the 
outfit from a manufacturer who has made the business a 
study. 

The care of the tin, in regard to keeping it free from 
dross or slag, is an important point in obtaining perfect 
work, and will be referred to in its proper place, 

TOOLS AND KETTLES. 

The tools employed in handling the work are very 
simple in construction. They consist of w'ires formed 
into various shapes, perforated ladles or baskets made 
from sheet iron or wire cloth, and tongs with the jaws 
formed to adapt themselves to the various articles it is 
designed to handle with thern. Those illustrated by Fig. 
13 in chapter on galvanizing will be found useful and all 
that will be required in many cases. The ingenuity of 
the operator will readily suggest what is required for the 
work in hand. 



/ 



46 GALVANIZING AND TINNING. 

The number of tinning kettles to be used depends alto- 
gether on the class of goods to be tinned. The most com- 
mon kinds of hardware specialties can be tinned very sat- 
isfactorily by the use of a single kettle of tin, while the 
better class of tinning, such as saddlery hardware, iron 
spoons, etc., require, in order to get the best results, two 
kettles, and three may be employed to good advantage. 

Where a plant is fitted up to do a fine grade of tinning 
the kettle used to give the castings their first coating of 
tin is designated as the " roughing kettle." and the other 
kettle or kettles as the finishing. When the roughing ket- 
tle is used no particular care is necessary to have the ar- 
ticles come out smoothly coated or free from surplus tin, 
as the unevenness of the coating will be removed by their 
later treatment in finishing. The object of the roughing 
kettle is to give the iron a thorough coating of tin as 
rapidly as it is prepared to receive it, which prevents rust- 
ing. After the iron receives a thorough coating of tin it 
may be stored away until it is desired to finish it. 

For those having only a small amount of tinning to 
do it would not pay to invest in an expensive outfit of wet 
rolling barrels, and very good results can be obtained 
without them. We will say here that only a few of the 
large concerns engaged in tinning are so fitted and the 
work they turn out is of a nature that calls for the best 
results possible to obtain as regards smoothness and 
brightness of the finished work. 

A TINNING PLANT. 

In installing a tinning plant the convenient handling 
of the work should be given all the consideration possible, 
and the operator will find it a great help toward making 
his work easy, as well as to the advantage of his employer. 



TINNING. 47 

if he will make a study of the best methods and tools to 
employ in handling the various articles that come to him 
to be tinned. 

While it is our purpose to treat this subject in a man- 
ner that will enable a novice to make a successful begin- 
ning, the best results can, of course, only be reached by 
actual practice. With the principles and requisites nec- 
essary to perfection in results obtained well understood, 
there should be no trouble experienced by one of average 
mechanical ability in mastering the business. 

To make the different operations of preparing and tin- 
ning articles of malleable iron, wrought iron and steel 
easily understood, we shall treat each operation separately. 

While the illustrations we give will serve as a general 
guide in equipping a plant, it does not follow that they 
must not or cannot be changed to suit local conditions. 
It would be impossible to illustrate the exact course to be 
followed in individual cases, and those undertaking the in- 
stallation of a plant must be governed to a great extent 
by their requirements as they see them. 

It should be kept in mind in deciding what part of the 
factory can best be devoted to the tinning department 
that more or less gases and fumes prevail when the work 
is carried on. These gases and fumes are not only dis- 
agreeable to inhale, but are destructive to fine machinery 
and tools and to finished work. To the end that the work 
may not become a source of annoyance to those not im- 
mediately engaged in it and detrimental to machinery and 
goods, the plant should be located if possible in a build- 
ing by itself, taking good care to provide good ventilation 
and drainage. 

A room devoted to this work should not be less than 
10 feet in hight, and the kettles and acid tanks provide'l 



48 GALVANIZING AND TINNING. 

with hoods connected with the ventilators to carry off the 
gases. The hoods should, of course, be high enough not 
to interfere with the perfectly free movements of the 
operator. 

The illustrations given contemplate tanks of cypress 
or pine for containing the different solutions used in pre- 
paring and finishing the work, but oil barrels sawed in 
half may be employed for the purpose if they arc properly 
cleaned either by burning out the interior or washing in 
a hot, strong solution of soda ash and water. 

For heating the tin hard coal is best, as it gives the 
most even heat and is most easily controlled. Soft coal, 
coke, natural gas and even wood can, however, be em- 
ployed for the purpose. 

PLAN OF TINNING PLANT. 

We show in Fig. 25 a ground plan for a tinning 
plant for general work, except the -tinning of common 
cast iron. In this illustration A denotes the roughing 
kettle — that is. the kettle containing the tin used to give 
the work its first coating of tin ; B is the finishing kettle ; 
C is the tank containing muriate of zinc ; D is what is 
termed in the trade the " whipping box," which is simply 
an arrangement to prevent the drops of molten tin being 
thrown promiscuously over the room when the operator 
is shaking or swinging his work to free it from the sur- 
plus metal ; E is a tank made of sheet iron for containing 
the kerosene oil used in cooling the work, the intent being 
to have this tank surrounded by running water to keep 
the oil cool, the water being contained in the companion 
tank F ; G is a tank provided with a steam coil, the intent 
being to have the tank filled with clean hot water, in which 
to rinse the finished work before drying it off in the saw- 



TINNING. 



49 




50 GALVANIZING AND TINNING. 

dust, which is contained in the box H ; I and O are water 
tanks used for storing the work after it has been treated 
in the acid ; K is a tank containing muriatic or sulphuric 
acid; L and M are acid tanks, the use of which will be 
explained in the proper place ; N is a tank for containing 
an alkali solution, and it should be provided with a steam 
coil ; R R denotes a drain through the center of the room 
to carry off the waste water. A .sectional plan of this 
floor is given in Fig. 38. 

REMOVING SCALE AND RUST WITH SULPHURIC ACID. 

To enable -steel and wrought iron to take a coating of 
tin, the scale and rust must be removed. This is best ac- 
complished with a pickle composed of 1 part sulphuric 
acid to about 30 to 40 of water, bringing the solution to a 
temperature of about 150 degree F. 

If the articles are of such a shape that they pack 
closely together they must be stirred so that the acid will 
have free action on all parts alike, otherwise the scale or 
rust will not be affected on that part that is in contact with 
another piece, the result being that the acid \Vill burn the 
material first made clean before the scale is removed from 
the part in contact. 

In pickling sheets they must be placed in racks that 
will prevent one sheet lying against another. Sheets 
should be carefully inspected, and any spots that the acid 
has not touched must be removed with the aid of a sharp 
pointed steel. The shank of an old file ground to a point 
and hardened answers the purpose very well. 

If the articles are small, and it is desired to give them 
a fine surface, roll them in sand and water after remov- 
ing the scale and rust with the acid solution, and to fur- 
ther improve their surface give them a second rolling in 



TINNING. 51 

scraps of leather. The effect of roUing is to give the 
articles a smooth surface, and the smoother the surface 
obtained the smoother and brighter will be the goods after 
tinning. 

We do not wish it to be understood that the rolling 
operation is absolutely necessary to obtain a complete 
coating of the goods, as they will take the tin perfectly if 
that operation is omitted, but the appearance of the goods 
is greatly improved by the rolling, and when it is desired 
to obtain the best finish possible the rolling barrel must 
be employed. 

When the removal of scale and rust has been affected 
and the material is perfectly clean it should be stored in 
tanks containing clear water, there to remain until the 
operator is ready to put it through the subsequent opera- 
tions. Do not allow the work to remain in running water, 
as it will soon rust or oxidize if it is. 

The operator must not fail to examine the work fre- 
quently while it remains in the hot pickle to determme 
when the desired result has been obtained. If it is al- 
lowed to remain too long a time after the scale and rust 
have been removed the acid will attack the surface of the 
material and leave it rough and seamed. Imperfections 
caused by overpickling cannot be covered up by the coat- 
ing of tin, and the commercial appearance of the goods is 
injured. 

The removal of scale and rust can be accomplished by a 
pickle composed of i part muriatic acid to 15 to 20 parts 
of water, but the cost is greater and the result obtained no 
better. It is not advisable to use this acid for the 
purpose unless the amount of work to be treated is very 
limited. 

In Fig. 25 K represents the tank to be used for the 



52 GALVANIZING AND TINNING. 

purpose just explained, and I indicates the storage tank 
for the prepared work. 

CLEANING SANDY CASTINGS BY SULPHURIC ACID. 

Castings that have sand on them must be subjected to 
a treatment that will effectually remove it, as a perfect 
coating cannot be obtained if a particle of sand remains. 
The removal of sand can be accomplished by placing the 
castings on an inclined platform and keeping them wet 
with a pickle composed of i part sulphuric acid to 6 of 
water, until the sand is loosened enough to wash off by 
the application of water. From lo to 20 hours is re- 
quired to accomplish its removal and then a casting brush 
often has to be employed to get out all the little particles 
that are burned in where there are sharp angles. 

Rolling with plenty of sharp scratches or shot is the 
only sure way to obtain a perfectly clean casting, and we 
should never attempt to tin malleable castings in any con- 
siderable quantity without the aid of a rolling barrel. As 
in the case with articles of steel or wrought iron, the wet 
rolling barrel supplemented by the dry rolling in leather 
scraps fits the castings to take a beautiful coating of tin 
and a bright luster. 

The platform on which the castings are placed for 
pickling should have a tank placed under one end at its 
lowest point to catch the acid as it flows from the castings 
after each bailing operation. This pickling arrangement 
is designated as L in Fig. 25, and the tank designated as 
M can be used to store the prepared work until it is de- 
sired to give it the finishing treatments. 

CLEANING SANDY CASTINGS WITH HYDROFLUORIC ACID. 

We have given the course to be followed for cleaning 
sandy castings with sulphuric acid, because it may not al- 



TINNING. 53 

ways be possible to obtain hydrofluoric acid, and because 
hydrofluoric acid is a comparatively new agent in the 
business. Where it is possible to substitute this powerful 
acid for sulphuric acid it should be employed, as its effects 
are much more rapid and certain, and are less destructive 
to the castings. 

In employing hydrofluoric acid to remove sand make 
a solution for slow pickling in the proportion of i part 
acid to 30 of water. For quick pickling make the pro- 
portion I of acid to 20 of water. Immerse the castings 
until the sand is dissolved, which will be in from 15 min- 
utes to 3 hours, depending on the strength of the solu- 
tion and the tenaciousness of the sand. 

A good arrangement for doing this work is to have 
two tanks, one elevated by means of a bench or stand, so 
that the bottom of the upper tank will be a few inches 
above the top of the lower tank. Provide a hole in the 
upper tank so that when the plug is removed the solu- 
tion will escape into the lower tank and leave the castings 
uncovered by the solution. When all the solution has es- 
caped into the lower tank cover the castings with water 
until it is desired to remove them for subsequent treat- 
ments. The solution in the lower tank is ready to use on 
a fresh batch of castings. We do not show this arrange- 
ment in Fig. 25, as it can take the place of the sulphuric 
acid, designated as ]M in that illustration. 

REMOVING PAINT OR GREASE. 

If the work is greasy or has paint on it, it must be 
cleaned with a hot solution of caustic soda or soda ash 
and water. Make the solution very hot and strong, and 
immerse the work in it until it is free from all such mat- 
ter, after which rinse it thoroughly in clean water. This 



54 GALVANIZING AND TINNING. 

Operation should precede pickling when it is necessary to 
perform it. The tanks for this purpose are designated in 
Fig. 25 as N and O. 

TINNING WITH A SINGLE KETTLE OF TIN. 

As already stated, very good results can be obtained by 
simply using one kettle of tin where the commercial ap- 
pearance of the work is of secondary importance. Where 
only a single kettle is employed the tin should be main- 
tained at a temperature of about 500 degrees F., and the 
work may be cooled in hot water and dried off in saw- 
dust. 

The operations preliminary to dipping the work in the 
tinning bath are precisely what they would be if more 
than one kettle of tin was used. As these operations will 
be explained in connection with those for using two ket- 
tles we will not give them here. 

Where only a single kettle is employed more or less 
trouble will be experienced in keeping the dross or slag 
which rises to the surface of the tin from adhering to the 
work and in keeping the tin at a uniform temperature. 
The dross or slag must be removed from the tin fre- 
quently with a perforated skimmer, and when the black 
flux that forms on the surface of the tin from the muriate 
of zinc, in which the castings are dipped previous to im- 
mersing them in the molten tin, is present in sufficient 
quantities to interfere with drawing the work, it must 
also be removed in part. A small amount is beneficial to 
the work, but when it accumulates in a sufficient quantity 
to catch on the work as it is drawn out it is apt to stain 
the work and leave white streaks wherever it touches. 
The cooling water should also be kept clean and free from 
acid. If it is not the work is liable to rust. In Figs. 29, 



TINNING. 55 

30 and 31 'we show manner of bricking in a single kettle, 
the casting details being shown in Fig. 32. 

TINNING WITH TWO OR MORE KETTLES OF TIN. 

When the work has been made perfectly clean from 
sand, scale, rnst, grease or paint by some one of the treat- 
ments described, it is ready for the final operations. If 
the work is of a kind that will admit of its being strung on 
wires, use such wires as seem best adapted to the work 
in hand. For many kinds of work a piece of wire bent in 
the shape of a croquet wicket will be found just the thing. 
Good stifif wires should be used, and they should be long 
enough to allow plenty of room for the operator to grasp 
the ends without getting burned. That is to say, if you 
have 10 inches of tin in the kettle, make the wire 20 inches 
long, which will allow 10 inches of wire to be out of the 
tin where the operator can grasp it when he is ready to 
draw the work from the kettle. Provide plenty of these 
wires so that the handling of the work may be facilitated. 

String on wires as much of the work as you think you 
can handle comfortably, and put them, several strings at a 
time, into the alkali solution. The work may be allowed 
to remain in this solution for several minutes, or while the 
operator is filling more wires. From the alkali solution 
the work is to be passed into the rinsing tank, and care 
should be taken that all traces of the alkali are removed. 

When this is accomplished the work is to be given a 
few minutes' immersion in a solution of muriatic acid and 
water. This mixture should be in the proportion of i 
of acid to 4 or 5 of water in cold weather, while in warm 
weather 8 or 10 of water to i of acid will do the required 
work. The object of this dip is to remove any trace of 
rust that may have formed on the work. The tank for 



56 GALVANIZING AND TINNING. 

this purpose is designated as K in Fig. 25, and for many 
kinds of work, such as castings that have been cleaned by 
dry rolling and goods that have been made of material that 
has no scale on it, all that is necessary is to give it a few 
minutes' immersion in this solution. 

From this last dip of muriatic acid and water, which 
by the way should never be omitted, the work is to be 
dipped in muriate of zinc, which is the last dip previous to 
immersing it in the molten tin. Tank C, Fig. 25, is 
used to contain the muriate of zinc, which solution is made 
by dissolving scraps of zinc in clear muriatic acid. 

PASSING THE WORK THROUGH THE TINNING KETTLES. 

If two kettles of tin are in use, as shown in Fig. 25 by 
A and B, take a wire full of the work to be dipped and im- 
merse it while wet with the muriate of zinc in the kettle 
of tin designed to give the work its first coating. This is 
the roughing kettle, and is designated in Fig. 25 as A. 
Put several of the strings of work into the kettle and 
allow them to remain until the work is as hot as the tin. 
The tin in this kettle should be maintained at a heat of 
about 500 degrees F. 

After the work has remained in the first kettle the 
requisite time take a wire full in the left hand, and with 
a skimmer held in the right hand clear a space on the sur- 
face of the tin large enough to admit of the wire full of 
work being removed without any of the slag or flux ad- 
hering to it. Remove the wire full of work and pass it 
directly to the second kettle. It is not necessary to shake 
off the surplus tin when removing from the first kettle, 
but it is necessary to use care that none of the flux or slag 
is carried over to the second kettle on the work. 

Retaining hold of the wire containing the work the 



TINNING. 



57 



Operator allows it to remain in the second kettle for the 
fraction of a minute until the heat of the work attained in 
the first kettle is reduced to about the temperature of the 
tin in the second kettle, which for most purposes should be 
about 400 degrees F. \^ery small articles may require that 
the tin in the second kettle attain a temperature of 450 
degrees F. A much higher heat will cause the tallow, 
which is on the second kettle, to a depth of >4 to i inch, to 
ignite. When the work is in the condition named draw 
it quickly from the tin, and after a few rapid swinging 
motions to free it of surplus metal plunge it into a tank 
of kerosene oil, using a motion calculated to keep the ar- 
ticles from sticking together. A little practice will soon 
determine what motion is best adapted to keep the ar- 
ticles separated and also prevent any lumps of tin form- 
ing on the work. 

D in Fig. 25 denotes the position of the box provided 
to catch the drops of tin that are thrown from the work 
as the operator swings it to and fro. E denotes the tank 
for containing the oil used for cooling, as already ex- 
plained. The tank containing this oil should be sur- 
rounded by water to prevent the oil heating to a point 
where it would ignite. 

The work should be allowed to remain in the oil long 
enough to set the tin, and it should then be thrown into 
fine sawdust to clean it of the oil. If the articles are very 
heavy it may be necessary to plunge them into cold water 
from the oil. 

Tf the work cannot be strung on wires a " basket " may 
be used for dipping it. The basket may be of sheet iron, 
in which case it should be provided with plenty of holes 
to show the tin to pass off. or it may be made of wire net- 
ting with a mesh sufficiently small to prevent the work 



58 GALVANIZING AND TINNING. 

falling through. Fig. 13 illustrates the shape of these 
baskets, which are designated as A and B. Nails, tacks, 
rivets and all similar articles are dipped in the tin by 
means of these baskets. Tongs are also used for handling 
heavy articles, but those used in the tin should not be used 
for cooling the work, as they would mark it. The tongs 
used for cooling should not be put into the molten tin. 
Their shape may be varied to suit the form of the article 
handled. 

TINNING WIRE IN COILS. 

In large manufacturing establishments machinery is 
employed whereby several strands of wire are passed 
through the tinning kettle simultaneously. To do the 
work on a small scale, provide reels that will accommo- 
date a coil of wire. Place one of the reels in a position 
where the black wire will pass, as it is uncoiled, through 
a tank containing muriate of zinc, and then through the 
kettle of tin. The other reel is placed in a position where 
it will take up the wire as it passes through the tin. The 
reel used to draw the work through the kettle must, of 
course, be provided with an arrangement for turning it, 
and a device to hold the wire under the muriate of zinc 
and also under the tin as it passes from one reel to the 
other must be employed. As the necessary arrangement 
will readily suggest itself we do not think it necessary to 
illustrate it. 

At the point where the wire leaves the molten tin a 
piece of tow is twisted around the strand, sufficiently 
tight to wipe off the surplus metal, which flows back into 
the kettle. If the wire is very heavy it must be made to 
pass through water after it leaves the tin, the water tank 
being placed where the wire will not enter it until it has 



TINNING. 



59 



passed through the bunch of tow used to wipe off the 
surpkis metal. 

If the wire is covered with a heavy scale or rust it 
must be cleaned in sulphuric acid the same as any other 
work. If it is bri,e:ht wire all that is necessary is to im- 
merse it in a solution of muriatic acid and water, i part 
acid to 6 of water. If wire is to be tinned in quantity a 
long shallow kettle is best adapted to the purpose. 

TINNING STEEL SPOONS AND SIMILAR ARTICLES. 

For this purpose provide a good sized kettle for 
" roughing " the work — that is, for giving it a prepar- 
atory coating. For finishing the work use small kettles. 
A kettle 15 inches long, 8 inches wide and 6 inches deep 
is ample for work of this kind. We refer to a plant fitted 
especially for this business. The work can be done in an 
outfit such as we illustrate by Fig. 25, but large finishing 
kettles are not as well adapted for this business as small 
ones, as the tin in a large kettle is apt to become dull in 
color by constant use, while in a small kettle the tin is 
turned over more rapidly, which allows it to hold its color 
much better. 

The articles should be rolled in tumbling barrels 
with scraps of leather and then carefully cleaned in 
an alkali solution. After rinsing off the alkali they should 
be immersed in quite a strong solution of muriatic acid 
and water for five or ten minutes, and then dipped in the 
roughing kettle by means of a wire basket, first dipping 
the work in a solution of muriate of zinc. As soon as 
they are thoroughly coated shake them out of the basket 
in such a way as will insure the separation of as many as 
possible. It makes no difference whether thev come 



So GALVANIZING AND TINNING. 

smooth or not so long as they are thoroughly coated. 
The smoothness will come in the finishing operation. 

To finish the goods take them, a piece at a time, in a 
pair of tongs adapted to hold them and immerse in the 
finishing kettle, the tin in which is covered with beef tal- 
low to the depth of about ^ inch. As soon as the article 
reaches the same heat as the tin remove it and allow it to 
cool enough so that the tin will not run, after which wipe 
up the goods in flour. 

RETINNING. 

This branch of the business is comparatively simple, 
since no pickling is required. An outfit for doing the 
work usually consists of the three kettles — one for rough- 
ing the work and two for finishing. The roughing ket- 
tle is usually set up by itself, although it may be con- 
tained in the same brick work with the finishing kettles. 

For retinning, kettles shaped like those used for sweat- 
ing zinc dross are best adapted for the work, and the man- 
ner of setting is practically the same. They should be 
co\'ered with a hood to catch the smoke and fumes which 
are constantly rising. The hood should be constructed 
to leave one side open so that the operator has free access 
to the kettles from one side. A view of a " tinning stack " 
resembles an open grate or the fire place of olden times, 
the brick setting to the kettles being about the hight of an 
ordinary work bench. 

The finishing kettles are kept covered with beef tal- 
low and palm oil, and care must be taken to prevent any 
dross or slag being carried over from one kettle to the 
other in the operation of passing the work from kettle to 
kettle. When large articles are being treated, like pressed 



TINNING. 



61 



dishpans, a swab of hemp is often used to free the article 
from dross before removing it to the last kettle. 

In drawing the article from the finishing kettle the 




Fig. 26.— End Elevation of Brick Work for Setting Two Kettles, 




Fig. 27.— Vertical Section through Fig. 26 at A\ A\ 

motion should not be too rapid. The piece should be held 
in one position and the drop of tin that forms at the low- 
est point removed by passing a piece of round iron along 



62 



GALVAXIZTNG AND TINNING. 



the edge. One end of this rod of iron is kept in the kettle 
of tin so that it is always ready for use. 

When the tin has " set," the article is passed to the 




Fig. S8. ^Horizontal Section through Fig. S6 at B\ B\ 




Fig. 29.— End Elevation of Brick Work for Setting Single 

Kettle. 

" bench " to be rubbed in flour. In large establishments 
girls arc mostly employed to clean the work with flour 
after it is tinned. 



TINNING. 



63 



The heat of the tin must be gauged to a nicety. If 
too hot the tallow will ignite and the work come out yel- 
low. If too cool the coating will be heavy and will not 
flow smoothly. 

It is perhaps unnecessary to say that in case rust has 




Fig. SO.— Section through Fig. 29 at A\ A\ 




Fig. 31.— Section of Fig. 29 at B\ B\ 



formed on the work from any cause it must be removed 
with acid the same as from any other work. Preparatory 
to dipping in the roughing kettle the work must be dipped 
in muriate of zinc. 



64 



iALVANIZING AND TINNING. 



SETTING RETINNING KETTLES. 



Kettles for retinning are set in a variety of ways, and 
hardly any two plants have the same arrangement of kettles 
or other apparatus. The principal point to consider in 






B 



















"XS" 



D^ 



Fig. S2. — Details of Tinning Kettle. 

bricking in kettles for retinning and, in fact, those for any 
purpose, is to place the fire and ash pit doors where thev 
will not interfere with the working of the kettles while the 
fires are being attended to. 



TINNIxVG. 65 

We give in Figs. 39 and 40 perspective views of the 
brick setting of a retinning stack. Fig. 39 shows the ket- 
tles in position, and Fig. 40 is a view of the back of the 
stack, showing the fire and ash pit openings. 

In these illustrations the entire stack is represented as 
being of brick. This plan is undoubtedly the most eco- 
nomical in the end, although many stacks are inclosed 
with sheet iron about the brick work surrounding the 
kettles. We think the perspective views will enable one 
to construct a stack without our giving the entire arrange- 
ment in detail, as we do in Figs. 26 to 31, inclusive. 

Fig. ^2 shows the casting details for setting kettles as 
represented by Figs. 26 to 31, inclusive. A gives a 
top, side and end view of the kettle ; B shows the coping 
plate : C is the grate in detail ; D is the front bearing bar 
in detail, and E the back bearing bar. The position of 
each piece is designated by a corresponding letter in Figs. 
26 to 31, inclusive. 

Fig. 26 is an end elevation of the brick work, Fig. 2y 
is a vertical section of Fig. 26 at A' A' and Fig. 28 is a 
horizontal section of Fig. 26 at B' B'. Figs. 29, 30 and 
31 show the manner of bricking in a single kettle. 



TINNING COMMON GRAY IRON. 

The tinning of common gray iron castings has become 
quite an extensive industry in the last seven or eight years. 
Previous to this time there were only one or two parties in 
the country able to do the work with any degree of suc- 
cess. While manufacturers had long recognized the fact 
that tin was a much more desirable metal tlian zinc for 
coating certain articles of culinary use the want of a cheap 
and practical process for tinning on gray iron precluded 
their giving the matter serious attention. 

The author perfected a method in 1891. a full descrip- 
tion of which will be given in this article, that proved a 
practical success, and to-day it is almost impossible to sell 
zinc coated articles that are to be used in the preparation 
of food. 

In addition to the uses to which tinned gray iron is 
put by the manufacturers of kitchen and other hardware 
specialties, it has been found of great advantage to give 
articles of cast iron that are to be copper or brass plated a 
coating of tin previous to plating them. The advantages 
come from the lessened quantity of material necessary to 
use in electroplating, the preventing of " leaking " or 
'' sweating," so common where the plating is deposited 
directly on the bare casting, and also in giving the articles 
the appearance of spelter or brass castings. 

By this process gray iron castings are prepared for 
tinning by rolling them in a solution of muriatic acid, sal 
ammoniac and water, the rolling barrel being constructed 

60 



TINNING. 67 

to retain at a high pressure the gas formed by the chem- 
icals used. The use of this barrel makes it desirable to 
locate the tinning plant in a building by itself, as the gas 
generated is constantly escaping, carrying with it quan- 
tities of the solution. At the best the barrel room for 
gray iron tinning is a wet, dirty place, and the entire op- 
eration requires the use of considerable water. 

DESCRIPTION OF TINNING PLANT. 

In erecting a building for this purpose particular atten- 
tion should be paid to ventilation and drainage. A plan 
for constructing a floor, with a view to perfect drainage, 
is shown by Fig. 38. The arrangement of the outfit is 
shown by Fig. 33, in which A is the rolling barrel for pre- 
paring the castings for tinning. B is a tank to receive the 
castings after they have been treated in the rolling barrel 
A. This tank should be provided with trucks, and a 
track should be laid so that the tank can be run under the 
rolling barrel to receive the prepared work. C is a tank 
for storing the prepared castings previous to further treat- 
ment, as hereafter described ; D,E, F and G are divisions of 
one common tank ; D is to contain an alkali solution, and 
is to be provided with a steam coil, as shown, to heat the 
solution ; E is a compartment for containing water for 
rinsing; F is to contain an acid solution; G is for the 
muriate of zinc ; H is the roughing kettle of tin ; K is the 
finishing kettle ; L is the oil for cooling the work. The 
arrangement of this tanR was explained in the chapter on 
general tinning ; M is a wooden tank large enough to ac- 
commodate the iron tank L and allow it to be surrounded 
with water ; N is a tank for containing hot water, in which 
the tinned work is dipped to remove any traces of oil or 
acid; it is provided with a steam coil, as shown; O is a 



68 



GALVANIZING AND TINNING. 
3r 




8 

I 

CO 

Si 

•2. 

s 






o 
C5 






TINNING. 69 

box to contain sawdust for drying off the work when 
it comes from the hot water contained in the tank N ; R R 
is a drain for carrying oft the waste water and S S are 
the tracks for moving the tanks B and C ; T is a tank for 
containing a sohition of hydrofluoric acid, to be used as 
hereafter described, and U is a storage tank. It is per- 
haps needless to say that the ground plan may be changed 
to suit local conditions. 

Only the most simple tools are required, which may 
be varied by the ingenuity of the operator to suit existing 
conditions of work. We give a sketch showing the most 
common in Fig. 13. 

GENERAL CONSIDERATIONS. 

In preparing gray iron castings to take a coating of 
tin there are several essential things to be taken into con- 
sideration : the quality of the iron, the form of the cast- 
ings, their condition when they come to the tinner, and if 
cored, the nature of the cores used. 

Hard iron needs a longer preparation than soft iron 
and a longer immersion in the molten tin. Castings that 
are made from patterns not designed with a view to avoid- 
ing sharp angles, in which the molding sand can find lodg- 
ment, are much more difficult to prepare than those made 
from patterns free from these obstacles. It is, of course, 
not always possible to do away with sharp angles in mak- 
ing patterns for castings that are designed to be tinned, 
but whenever possible they should be avoided in the inter- 
est of easy cleaning from sand and perfect coating of the 
w^ork. 

Castings that have been freed from sand by the use of 
sulphuric acid require a special preparation before they 
will take a perfect coating of tin, and the use of this acid 



70 



GALVANIZING AND TINNING. 



should be avoided if possible. Cored castings made with 
cores in which rosin has been used must be treated dif- 
ferently from those made with an oil or glue core. For 
the intelligent understanding of the different conditions 
we give the specific course to be followed in each case. 




Fig. Slf,. — Top View of Rolling Barrel with Receiving Tank 

in Position. 

The perfect coating of gray iron requires the use of 
two tinning kettles, and where castings are to be tinned 
previous to electroplating three kettles of tin should be 
used to insure .the smoothest coating and the brightest 
luster. 

TUMBLING BARREL. 

An outfit for preparing and tmning cast iron consists 
of a tumblintr barrel, constructed in accordance with the 



TINNING. 



71 



plan shown by Figs. 34, 35, 36 and 2,7- The points 
whereni this barrel differs from the ordinary wet rollino- 




Fig. SS.Side View of Fig. 34, 




—J -^'^ T 



Fig. S6.—Gear End of Fig. S4. 

barrel are that it is built very heavy and strong-. It is 
provided with valves for the escape of the gases generated 



72 GALVANIZING AND TINNING. 

by the chemicals used, and the opening where the barrel is 
filled is arranged to close tightly. 

For general work we prefer a barrel 48 inches long 
and 24 inches in diameter. The shell we make of ^-inch 
boiler iron, and use cast iron heads iVz inches thick. The 
manhole cover we make i inch thick, and have it well 
ribbed to give additional strength. 

Fig. 34 is a top view of the barrel, and it also shows 
the receiving tank H, designated in the ground plan, Fig. 
33, as B. 

Fig. 35 is a side view of Fig. 34, and Fig. 36 is a view 
of the gear end of the barrel. 

Fig. 37 gives the details of the barrel, in which A is an 
end view of the trunnions B, and C and D are the pillow 
blocks supporting the barrel and E those for the pinion 
shaft ; F is the valve for the relief of gas and G is a view 
of the end of the barrel on which the valves F are placed. 

Two or more kettles (depending on the nature of the 
work) set after the plan illustrated by Figs. 26, 27 and 28, 
and various tanks built after Fig. 12, complete the outfit. 

The first operation in preparing the castings for tin- 
ning is to free them from sand. This is best accomplished 
by the use of the ordinary tumbling barrel, which gives 
the castings a smooth clean surface while doing the work 
of removing the sand. Where the castings are of a na- 
ture to prevent their perfect cleaning by tumbling, the 
sand should be removed by a solution of hydrofluoric acid 
and water. Sulphuric acid will do the work, but in a 
much inferior manner and to the injury of the castings in 
relation to their ready and perfect coating. The reason 
for this is easily understood. Hydrofluoric acid acts di- 
rectly on the sand, dissolving it rapidly without attacking 
the iron to any great extent. The action of sulphuric acid 



TINNING. 



n 





1 .^ 


?q r 1 








O |l 
li 


0) 


D 


r^,' ' 


m ;;^ 





Fig. 37.— Details of Rolling Barrel 



74 



GALVANIZING AND TINNING. 



is the reverse, the iron being dissolved on the surface, 
causing the sand to fall oft", while the sand itself is not 
affected. 

FREEING GRAY IRON CASTINGS FROM SAND BY HYDRO- 
FLUORIC ACID. 

While this operation is nearly the same as the one 
given for cleaning malleable iron by the use of this acid 







Fig. SS. — Detail of Floor Drainage. 



we wish to impress the operator with the fact that in 
treating gray iron with acid of any kind, for the purpose 
of preparing it for tinning, much more care must be ex- 
pended in the operation than with malleable iron, as the 
overpickling of gray iron leaves the surface soft and 
gummy, in which condition it will not take a coating of 
tin, and it is no easy matter to get it in a condition where 
it will. 

For quick cleaning of sandy castings by the use of 
hydrofluoric acid the preparation should be i of acid to 



TINNING. 



75 




Fig. 39.— Front View of Retinning Stack. 




Fig. 40.— Back and End Vieiv of Fig. 39. 



76 GALVANIZING AND TINNING. 

20 of water. For slow cleaning, which ir necessary on 
castings having sharp angles into w^hich the molding sand 
has burned, use the acid in the proportion of i of acid to 
30 of water. The castings may remain in this solution 
until the sand is dissolved, after which, provided they 
have not been made with rosin cores, they are ready to be 
placed in the tumbling barrel used to prepare them for 
tinning. If rosin cores have been used they are to be 
treated in a special way, which will be explained in its 
turn. 

A good arrangement to clean sandy castings with 
hydrofluoric acid is to have two tanks (oil barrels sawed 
in half will answer), one elevated above the other by 
means of a stand or bench, so that the top of the lower 
tank will be 3 or 4 inches below the bottom of the ele- 
vated tank. Bore a hole in the side of the upper tank 
close to the bottom and provide a plug. Place the cast- 
ings in the upper tank and cover them with the solution, 
which has previously been mixed and is contained in the 
tank below. When the castings have been completely 
freed from sand remove the plug and allow the solution to 
escape into the tank below, where it remains until re- 
quired for use again. No specific rule can be given as to 
the time required to clean the castings, and it is not neces- 
sary, as an examination of the work from time to time 
while under treatment will determine when they are clean. 
Castings on which a light sand is attached might be clean 
after 15 minutes' immersion in the solution, while castings 
having a heavy coating of sand, or on which the sand has 
burned, might require three or four hours. 

If the nature of the sand attached to the castings 
makes it seem probable that they will require a longer im- 
mersion in the acid, weaken it by adding water to a point 



TINNING. 77 

where there can be no possible danger of the castings 
being affected in the way mentioned in the beginning of 
this subject. 

T and U in Fig. 33 are the tanks designed for treat- 
ing the castings with hydrofluoric acid. If it is found 
impracticable to get this acid the work may be done with 
sulphuric acid, in which case the arrangement for its use 
will occupy the same position as designated for hydro- 
fluoric acid. 

CLEAXIXG SANDY CASTINGS W^ITH SULPHURIC ACID. 

If sulphuric acid is used to free the castings from sand 
place them on an inclined, raised platform, which platform 
should be of a size to accommodate the intended produc- 
tion and arranged to allow the solution to flow back into 
the tank placed at the lowest point to receive it. Make the 
solution in the proportion of i of acid to 6 of water, and 
keep the castings wet with this solution until the sand is 
readily removed by the application of water. Gray iron 
castings cleaned in this way will have a soft, gummy de- 
posit on the surface, and will not take as perfect a coating 
of tin as castings cleaned by dry tumbling or by the use 
of hydrofluoric acid, and they must be given a special 
treatment before tinning, which will be described in con- 
nection with the treatment for castings made with rosin 
cores and hard and greasy castings. 

After the castings have been freed from sand in some 
one of the ways described, provided they are not exces- 
sively hard castings or made with rosin cores, are not 
greasy or " pickled " with sulphuric acid, and have not 
been faced with black lead facing, then they are ready for 
tumbling in the solution of muriatic acid, sal ammoniac 
and water. If any of these conditions exist they must 



78 GALVANIZING AND TINNING. 

be given a treatment in a bath of hot caustic soda or 
soda ash. 

THE USE OF A HOT ALKALI BATH IN CERTAIN CASES. 

If castings have been overpickled — that is, left in the 
pickle until the surface has become covered with a soft, 
gummy substance — or if rosin cores have been used in mak- 
ing the castings or black lead facing used to give a 
smooth surface, or if grease or paint is present, they must 
be immersed for several minutes in a boiling solution of 
caustic soda or soda ash. Make the solution very strong, 
and see that the strength is maintained by adding fresh 
material as needed. 

After this treatment the castings must be thoroughly 
washed with clean water before they are placed in the 
barrel used to prepare them for tinning. D in Fig. 33 
designates the tank to be used for the hot alkali solution 
and F in the same illustration is the tank used for rinsing. 

PREPARING THE CASTINGS IN THE GAS BARREL. 

The details of cleaning having been carefully attended 
to, place the castings in the tumbling barrel, together with 
a quantity of ordinary " stars," such as are used in dry 
tumbling, being careful to load the barrel in such a way as 
to prevent breaking or w^earing the corners of the castings. 
Tea kettles should be filled full of the stars or shot before 
placing them in the tumbling barrel and light, delicate 
castings should be packed tight enough to prevent break- 
ing. Stars or shot sufficient to fill the barrel about one- 
fourth full will be found the most desirable quantity for 
ordinary work, although on hollow ware much more is 
needed, or enough to take up nearly all the vacant space. 
After the barrel has been loaded in the way described put 



TINNING. 79 

in sufficient water to fill it about three-fourths full, then 
add to the barrel 15 pounds of commercial muriatic acid 
and 2 pounds of gray granulated sal ammoniac. The 
barrel is now ready to be closed and started, presuming 
that the operator has examined the valves to see that they 
are in perfect working order previous to loading the 
barrel. 

After the barrel has been in motion from 5 to 15 min- 
utes, depending on the temperature of the water used, 
there will be formed sufficient gas to cause the valves to 
open. The escape of gas will be accompanied by quanti- 
ties of the solution, and the end of the barrel on which 
the valves are placed should be inclosed, unless the barrel 
is set up in a different room from the rest of the outfit. 

The time that the castings should be rolled in this solu- 
tion varies from two and one-half to five hours. Soft 
smooth castings will take a nice coating after a prepara- 
tion of two and one-half hours, while to obtain the same 
results on hard iron, iron cleaned by the use of sulphuric 
acid, hollow ware and tea kettles and castings having a 
black lead facing, five hours in the barrel are necessary. 
It is safe to say that three and one-half hours will properly 
prepare ordinary castings, the barrel making 40 revolu- 
tions a minute. For hollow ware, tea kettles and very 
delicate castings the barrel should not attain a speed of 
over 30 revolutions per minute. After the castings have 
been rolled in the solution the required time open the 
barrel and cover its contents with water immediately. 
Do not let any time be wasted in getting the castings cov- 
ered with water, as a slight exposure to the air will cause 
them to oxidize and prevent them from taking the tin. 
If the castings are properly prepared—that is, if they 
have been rolled in the solution long enough — they will be 



So GALVANIZING AND TINNING. 

in such a condition after rinsing that they will not soil a 
white cloth to any extent. 

As soon as the operator has determined whether the 
castings will tin properly (which is done by putting one or 
two of the pieces through the regular treatment) he will 
proceed to dump the contents of the barrel into the receiv- 
ing tank, located directly under the barrel. This tank is 
designated in Fig. 33 as B, and should contain about one- 
third more cubic feet than the rolling barrel. From this 
receiving tank the castings should be removed to the stor- 
age tank designated C in Fig. 33. A good sized coke 
fork is best for handling the castings from tank to tank 
as it lets the shot or stars fall to the floor and separate 
from the castings. 

In placing the castings in the storage tank care should 
be taken to have those with depressions or cavities go 
under the water with the depressions or cavities up. In 
other words castings of a shape that would admit of a 
particle of air being retained should be so placed that no 
air will be retained. If this occurs there will be a rusty 
place form on the casting to which the tin will not adhere. 
Should it be found that the castings are not properly pre- 
pared the barrel should be recharged by adding 6 pounds 
of muriatic acid and allowed to run about an hour longer. 

The important point to be kept in mind in preparing 
cast iron for tinning is that the surface of the iron must 
be made perfectly clean. Not only clean from sand and 
rust, but from every foreign substance. It may seem to 
the reader that we are dwelling on this point unneces- 
sarily, but only by the most careful attention to the proper 
preparation of the castings and in keeping them in the 
same clean condition until they receive the first coat of tin 
can perfectly satisfactory work be obtained. 



TINNING. ol 

If the iron is allowed to roll in the solution too long a 
time the surface becomes soft from the action of the acid, 
and the tin will not take. The same trouble will be ex- 
perienced if the solution in the rolling barrel is too strong, 
or if the castings are allowed to remain in the solution 
too long after they are rolled. In rolling the castings cal- 
culation should be made to complete the work before the 
stopping of the power at noon and night. Three and one- 
half hours being required on an average to prepare most 
iron in the rolling barrel, it is easy to arrange to start the 
barrel in time to complete one batch in the morning and 
one in the afternoon. This would furnish work enough 
to keep two hands engaged, although one set of kettles 
would take care of all the iron that could be prepared in 
a barrel the size we show — viz., 2 feet in diameter by 4 
feet in length. 

If the castings are quite soft and clean three batches 
may be prepared in ten hours, in which case the second 
batch should be in the barrel in time to give it at least 
one hour's rolling before the power is stopped at noon. 
When a batch of iron is left in the barrel during the noon 
hour, leave the barrel closed, and in a position where one 
of the valves will be up or the opening above the solution 
in the barrel. Unless this is done the valves may open 
and allow the solution to escape, necessitating recharging 
the barrel. If the batch is not completed in season to 
remove it to the storage tank before the time for stopping 
the power at night, remove the cover, and allow enough 
fresh water to flow into the barrel to displace at least half 
of the solution, and leave it in that condition until morn- 
ing, taking care that the valves do not leak, that the iron 
is completely covered, and that the water is not left run- 



82 GALVANIZING AND TINNING. 

ning, as iron will rust in running water even if the water 
covers it. 

In rolling a batch of iron it will often be found that 
a black foam will rise to the surface of the solution when 
the barrel is opened. This is from the iron dust left on 
castings that are cleaned by dry tumbling, and it will also 
be found in preparing castings that have been faced with 
foundry facing of any sort. When this foam or scum 
is present, let water flow into the barrel, with the opening 
in such a position as to allow the objectionable matter to 
pass ofif. The first one or two batches prepared in a new 
barrel arc liable to give trouble in tinning unless the in- 
side of the barrel, with the shot to be used, is cleaned with 
a strong alkali solution. The simplest way is to put the 
shot into the barrel, and after filling it about half full of 
strong, hot alkali solution, close the barrel, and allow it 
to run an hour or more, after which the interior of the 
barrel and the shot used should be rinsed with plenty of 
clean water. 

Where castings are tinned for the purpose of electro- 
plating them it is desirable, if an extra smooth surface is 
desired, to give them a rolling in gravel and water in the 
ordinary wet rolling barrel, although this treatment is 
not necessary in order to prepare them to take a coating 
of tin. In treating castings in this way use a coarse hard 
gravel, and some castings may be rolled 20 to 30 hours 
to good advantage if the barrel is properly loaded. 

It sometimes happens that castings are encountered 
that have a ground work of delicate design into which 
the sand has burned. If such are placed in the rolling 
barrel with a good quantity of shot and given two or 
three hours' rolling in a solution of hydrofluoric acid and 
water, i part acid to 75 or 100 of water, they will be 



TINNING. 83 

cleaned very nicely. Where this is clone let the hydro- 
fluoric solution run out of the barrel before charging it 
with the regular solution of muriatic acid, sal ammoniac 
and water. 

The operator must bear in mind at all times, as a safe- 
guard against accident, that he must see that the valves 
on the rolling barrel are in working order previous to 
loading the barrel. These valves should be adjusted to 
open at a pressure of 40 pounds. If by reason of a leak 
in any part in the barrel gas is not generated the work 
will not tin properly. Do not approach the barrel with a 
light at any time when the gas is escaping, or at any time 
when the gas is being generated in the barrel. If after 
stopping the barrel it is found that the valves leak, as 
they may from becoming clogged, stop the leak, as the 
solution will escape, allowing the work to oxidize. Badly 
oxidized castings will not tin. The solution contained 
in tank F, Fig. 33, is calculated to remove a light oxide. 
but castings that are heavily oxidized must be rerolled. 

COATING THE CASTINGS W^ITII TIN. 

The tin in the kettles being at the proper heat for the 
work in hand, as specified later on, the operator takes a 
small quantity of the castings from the storage tank C. 
Fig. 33, and places them in the wire basket designated A 
in Fig. 13, taking care to place those having concave sides, 
holes or depressions so that none of the various solutions 
through which they are now to pass will be retained. 
The castings contained in the wire basket must now be 
immersed in the solution of caustic soda or potash, re- 
ferred to in connection with the treatment for greasy, 
hard or lead faced castings, which solution is contained in 
tank D, Fig. 33. This solution must be kept at the boil- 



84 GALVANIZING AND TINNING. 

ing point, and from one to two minutes is sufficient time 
to leave the castings in. The best plan for heating this 
solution is to have a steam coil in the bottom of the tank, 
as shown in the illustration, and to allow the exhaust steam 
to pass into the rinsing tank, which is placed directly be- 
side it, as shown in the ground plan. The rinsing tank 
is designated E in Fig. ;^7,. After the castings have stood 
in the alkali bath contained in tank D the desired time 
they are placed in the rinsing tank E until all traces of 
that solution are removed. This will take the fraction of 
a minute provided a stream of water is kept flowing into 
the tank, as it should be. 

The next move is to immerse the castings in a very 
weak solution of muriatic acid and water, i part acid to 
40 of water. The castings must not be allowed to stand 
in this solution more than two or three seconds. The tank 
to contain this solution is designated as F in Fig. ^^.' 

Next place the castings in the tank G, Fig. ^^, which 
contains muriate of zinc, to which has been added 5 
pounds of gray granulated sal ammoniac for every gallon 
of the muriate. jMuriate of zinc is made by dissolving 
zinc in muriatic acid, allowing the acid to dissolve all the 
zinc it will. For the purpose of making this cut acid an 
earthen crock can be employed, or an oil barrel sawed in 
half will answer the purpose. 

The castings are now ready to be immersed in the 
molten tin contained in the first kettle and shown in Fig. 
33 at H. The tin in this kettle should attain a heat of 
500 degrees F., and this heat should be maintained during 
the time the kettle is in use. 

Before immersing the castings in this kettle the sur- 
face of the tin should be covered by a flux made by boil- 
ing a quantity of the muriate of zinc on top of the molten 



TINNING. 85 

tin, and adding quickly to the boiling mass a quantity 
of white granulated sal ammoniac. The sal ammoniac 
must be added by sprinkling it on before the acid is evap- 
orated by the heat of the tin. It will take a little time 
and experience before the proper consistency of this flux 
can be attained. The proper combination of this flux 
is one of the most essential points in the successful coat- 
ing of the cast iron in this first kettle of tin. If the flux 
is allowed to become hard and dry, as it soon will by con- 
tinued use unless careful and constant attention is given 
to it, the flux will adhere to the castings as they pass 
through it into the tin below, and thereby prevent them 
from coating. 

When it is found that the flux is becoming thick and 
lumpy add a sufficient quantity of the muriate of zinc and 
powdered sal ammoniac to cause the flux to boil up to a 
depth of y2 inch or more. When this result is obtained 
take a perforated iron skimmer and carefully remove any 
hard lumps and congealed matter remaining in the flux, 
allowing such as readily pass through the skimmer to re- 
main in the kettle. The purpose of this flux is to pre- 
vent the surface of the tin from becoming oxidized by 
exposure to the air, and also to prevent the hot metal 
from spattering and burning the operator when the wet 
castings come in contact with the tin. Keep carefully in 
mind that this flux must at all times be kept in a thin 
liquid condition, otherwise the succeeding operations 
through which the castings are to pass before they are 
completed will be unsuccessful. 

In placing the castings in this first kettle of tin care 
should be taken to get them immersed as soon as possible. 
If they are allowed to float on the surlace of the tin the 
muriate of zinc with which they are wet (for the purpose 



86 GALVANIZING. AND TINNING. 

of causing the tin to adhere) will dry off, and the tin will 
not adhere to that part of the casting left exposed. The 
work must be kept below the surface of the tin until it 
has become as hot as the tin itself, and until the tin has 
ceased to bubble or to be agitated by the castings that are 
immersed. This boiling or agitation will cease when the 
air is expelled from the iron and the flux that adhered to 
it as it passed through has risen to the surface of the tin 
again. 

The proper way to immerse the work in this first ket- 
tle of tin is to rest the handle of the basket containing it 
on the edge of the tin kettle, elevating the basket at an 
angle that will prevent it touching the molten tin until the 
operator is ready to have it. Cant the basket so that one 
of the lower corners will enter the tin first ; in other words, 
do not allow the bottom of the basket to come directly onto 
the surface of the tin, as the effect of having so much wet 
metal as the bottom of the basket presents come in con- 
tact with the molten tin will be an explosion, resulting 
most likely in the serious injury of the operator or any 
one standing near. When the basket is in the described 
position lower it carefully until i inch or 2 inches of the 
bottom and one side is immersed in the tin, then lower 
rapidly, but steadily, until the basket and its contents are 
completely immersed. 

At this point turn the basket completely over, bottom 
up, and, using the edge of the tin kettle as a rest for the 
handle, lift the basket from the tin. When the basket is 
free turn it bottom down and use it in that position to 
keep the castings it contained below the surface of the tin. 
Fill the kettle as full of castings as it will hold and allow 
them to be completely immersed. Several of the wire 



TINNING. ^7 

baskets may be employed to insure having a batch ready 
to immerse wlien the previous one is disposed of. 

It sometimes happens that the operator carelessly omits 
dipping- the work in the cut acid contained in tank G, Fig. 
^^ ; that is, he may attempt to immerse the work in the 
molten tin directly from tank D, E or F. Such neglect is 
dangerous and likely to be attended with serious results to 
the operator, from the hot metal spattering. 

There are many kinds of work that may be strung on 
wires and handled through the different stages without 
the use of the wire baskets. When wires are used the 
shape may be varied to suit conditions. While we show 
the most common in Fig. 13, the ingenuity of the operator 
must be employed in selecting those best adapted to his 
wants and in devising others for himself. 

The kettle being full as described, the castings must 
remain where they are from 5 to 15 minutes, or until they 
have taken a perfect coating of tin. If in this time they 
are not properly coated, some error has been committed in 
the previous operations and the work must be reroUed. 

What dross or slag forms in a tin kettle rises to the 
surface. A considerable part of this objectionable matter 
will be found in the first kettle, which must be removed 
before the work can be carried to the finishing kettle or 
kettles. To accomplish the removal of this dross or slag, 
floating on the surface of the tin, use a perforated, concave 
iron skimmer. The holes in the skimmer should be large 
enough to allow the clear tin to flow through freely, and 
care should be taken not to waste the flux in skimming out 
the dross. If the skimmer is canted edgewise as soon as 
the clear tin passes off the slag will adhere to the skimmer 
and the flux will flow back into the kettle. 

When all the slag has been removed grasp one of the 



88 GALVANTZTNG AND TINNING. 

castings with a pair of tongs and remove it with a quick 
motion from the tin. If wires have been employed and 
the work is strung, take one or more wires and remove in 
the same way to the next kettle, taking care that no flux or 
dross is carried along with the work. The temperature 
of the tin in the first kettle is much too high for finishing 
the work, and when the castings that are taken from this 
first kettle are exposed to the air they will be more or less 
yellow, depending on the heat of the tin. A bright yellow 
or golden color indicates too high a heat of the tin and 
must be avoided. A slight yellowish tinge indicates the 
proper heat. 

The tin in the second kettle, which is designated in Fig. 
33 as K, and which is, in most cases, the finishing kettle, 
must be maintained at a temperature of about 400 degrees 
F., and the surface kept covered to the depth of from ^ to 
I inch with pure beef tallow. Palm oil may be introduced 
into the tallow with good results, using of the latter about 
10 per cent. The operator retains the castings held by the 
tongs or wires immersed in this second kettle one or two 
seconds and then, with the tongs held in the left hand, he 
removes the piece from the tin. As soon as the piece is 
clear of the tin the operator grasps it with a pair of tongs 
held in the right hand, and with a few rapid swinging 
motions to free the article from surplus tin, he plunges it 
into a tank containing kerosene oil. If wires are being 
employed he swings the work to and fro rapidly to free it 
from the surplus tin, and when plunging it into the oil he 
must give the work a motion calculated to prevent the 
articles in contact from adhering to each other. 

The tank, which is designated in Fig, 33 as L, in con- 
nection with a companion tank M, should be of sheet iron 
and placed in the companion tank M with a view to having 



TINNING. 89 

a body of water surrounding it to keep the oil from becom- 
ing heated, as it soon would be from the hot castings 
constantly immersed in it. The work must be immersed 
in this oil long enough to set the tin and then immersed in 
the cold water contained in the companion tank M. 

If the tin in this last or finishing kettle is at the right 
temperature the work will be white and have a nice luster 
after it is cooled. If the work is rough and lumpy it indi- 
cates that the tin in the finishing kettle was not hot enough 
or that the work was kept in the air too long a time before 
dipping it in the oil. The tin in the finishing kettle 
requires very little fire to be maintained as there will be 
nearly enough heat in the castings when they come from 
the first kettle to keep the tin in the second at a proper 
heat. If the work is yellow after cooling in the oil, it may 
indicate too high a heat in the finishing kettle, or it may 
indicate that the casting was not kept in the finishing ket- 
tle long enough to bring the heat that the casting attained 
in the first kettle down to a point where the tin would not 
be yellow. 

The work will come out of the finishing kettle smoothly 
and brightly coated even when the temperature of that 
kettle is so low that if a piece of cold iron be put in the tin 
would adhere to it in a mass. The heat the castings attain 
in the first kettle makes it possible to run the finishing 
kettle at a very low temperature and it is desirable to do so 
on very heavy castings. Light castings require, of course, 
that a much higher heat be maintained in the finishing 
kettle than is necessary on heavy castings. The reason is 
apparent : Light castings must be exposed to the air a few 
seconds while the operator is switching ofif the surplus tin, 
and being light, they, of course, do not hold the heat long 



90 GALVANIZING AND TINNING. 

enough to allow the surplus tin to be shaken off without 
leaving rough, ragged edges. 

A great deal of ingenuity can be displayed by the 
operator in handling castings of various shapes in such a 
way that no lumps or bunches of tin will remain on the 
work after it is cooled. For example, in grasping the 
article to be cooled care should be used to find what part 
of the casting is best adapted to be taken hold of by the 
cooling tongs without marks of the tongs being left after 
the article is cooled. The tongs used for cooling should 
never be put into the tin kettle, as the heat of the casting 
would cause it to adhere to the tongs if they were tinned. 
After shaking off the surplus tin change the position of 
the casting so that the drop of tin, which will naturally col- 
lect at the lowest point, will flow back ontiD the casting and 
dip in the oil at once when this is s.ccomplished. 

A '* switching box " should be employed when 
" strung " work is being handled to catch the tin that is 
thrown from the work in the operation of " switching " 
it to throw off the surplus tin. This box is a very simple 
arrangement. Its position when in use is designated D, 
Fig. 25. Cover the interior of the box with heavy paper, 
as the hot tin will stick to the wood unless paper is used. 
The tin thus collected may be thrown into 'the kettle 
together with the paper when the tin is needed for use. 

When the castings have been finally cooled as already 
described, they should be immersed in a tank of boiling 
water to free them from oil and also to remove any trace 
of acid that may be on them. This final rinsing tank is 
designated X in Fig. 33. The water must be kept clean 
and at the boiling point at all times when in use. An 
ordinary foundry riddle with upright handles long enough 
to allow the operator to set the riddle, with the work to be 



TINNING. 91 

treated, into the tank without scalding his hands, may be 
employed to immerse the work in this tank. 

The castings should be dried off in clean dry sawdust, 
and for this purpose use sawdust made from pine or some 
soft wood, as hardwood sawdust will scratch the tinned 
surface. The drying box is shown at O in Fig. ^^. 

When three kettles of tin are employed, as they may be 
to good advantage in tinning work that is designed to be 
plated, the second kettle must be run at a temperature of 
450 degrees F. The surface of the tin in this kettle must 
be kept covered with an acid and sal ammoniac flux the 
same as the first kettle. The castings in the first kettle are 
to be passed in quantities to the second kettle, there to re- 
main until the first kettle is refilled. The same care must 
be taken not to allow any of the slag or flux that accumu- 
lates on the first kettle passing with the work to the second 
kettle, and the tin in the second kettle must be kept free 
from slag. 

The tin in the third or finishing kettle should be main- 
tained at a temperature of 400 degrees F., and the depth 
of the tallow increased to 3 or 4 inches. 

If three kettles are employed they should be square or 
round and arranged to fire from one side, instead of at 
the ends. 

The water in storage tank C. Fig. ^^, will in a short 
time become charged with the acid solution from the roll- 
ing barrel unless it is changed frequently. If much acid 
is present in the water it will impair the alkali solution 
into which the castings pass directly from the storage 
tank. If a few pounds of the alkali selected for use 
(caustic soda or soda ash) is added two or three times a 
week the alkali will do its work properly for some time, 
although it is best to clean out the tank and make the solu- 



92 GALVANIZING AND TINNING, 

tion Up fresh once in two weeks w^here it is in constant 
use. 

In rinsing the castings in tank E, Fig. 33, do not let 
them remain in a great length of time if water is flowing 
in, as iron will soon rust in running water. The solution 
in tank F, Fig. 33, should be made up fresh after 2 or 
3 tons of iron has passed through it, and, as already stated, 
the castings should not be allowed to stand in this solution 
more than two or three seconds. 

The solution of muriate of zinc contained in tank G, 
Fig. 33, should be deep enough to cover the castings con- 
tained in the wire basket used to immerse them in the 
first kettle, and the solution should be kept in good con- 
dition — that is, care should be taken not to allow it to be 
weakened to any great extent by the solution in tank F 
passing into it with the work. The tank containing this 
muriate of zinc should be lead lined and an inner lining 
of wood used to protect the lead lining. 

As it is almost impossible to make castings that have 
been imperfectly coated at the first attempt take a satis- 
factory coating of tin, the operator should give careful 
attention to details. 

It is possible by practice to keep the tin at a proper 
heat, but the operator will find more difficulty in doing 
this than any other one thing in the entire operation. That 
the proper heat be maintained is very essential, for if it is 
not, all previous care in preparing the iron will have been 
in vain. If too hot the flux on the first kettle of tin will 
evaporate or burn off, and the tin will not take to the iron. 
If too high a heat is reached on the kettle containing the 
tallow, tl e tallow will be set on fire. As a help to a nov- 
ice and, in fact, to an experienced man, we recommend 
the use of a pyrometer, one for each kettle. The expense 



TINNING. 93 

of providing them is not to be considered in comparison 
with the advantages obtained. 

The kettles for containing the tin may be, and usually 
are, of cast iron, although fire box steel is often employed 
to make oblong kettles. 

A floor space of 20 x 40 feet will accommodate a tin- 
ning plant running two rolling barrels. If possible, the 
plant should be located handy to power and with a view 
to obtaming easy and perfect drainage. If necessity com- 
pels the setting up of the plant in the factory building 
above the ground floor, as is sometimes the case, the floor 
of the tinning room must be so constructed that leakage 
into the room or rooms below will be prevented. 

The dross or slag formed in the kettles should be 
stored away until a suflicicnt amount is accumulated to 
make profitable the remelting of the slag for the purpose 
of reclaiming what pure tin is in it. For the purpose of 
remelting this dross the pure tin can be removed from 
the kettle H, Fig. 33, and the dross melted up in it. When 
the entire mass is in a molten state, and at a temperature 
of about 550 degree F., bail off the liquid tin into cast 
iron pans provided for that purpose, and what dross re- 
mains into separate pans. This tin dross has a market 
value of from 40 to 50 per cent, of the price of pure tin. 

With the addition of tanks for containing acids a 
plant built to tin cast iron is adapted to all descriptions 
of tinning, except retinning of tinware and the tinning of 
sheets. 



OCT 19 1900 



LIBRARY OF CONGRESS 




